Signal correction method for pulse type terahertz system

Abstract

The invention discloses a signal correction method for a pulse type terahertz system, and relates to the technical field of terahertz waves. After frequency spectrum data of terahertz signals are obtained through a terahertz waveform standard device, a distortion coefficient is calculated, frequency domain data, obtained in a terahertz system, of the terahertz signals are corrected through the distortion coefficient, and then undistorted terahertz time domain waveforms are obtained through inverse Fourier transform. The problems that in a current pulse type terahertz system, the inherent influence elimination cost of the system is high, and signals are prone to distortion are solved.

Description

Technical Field

[0001] This application relates to the field of terahertz wave technology, and in particular to a signal correction method for pulsed terahertz systems. Background Technology

[0002] Terahertz waves are electromagnetic waves with wavelengths between microwaves and infrared light. Due to their unique frequency characteristics, they have been widely used in communication technology, material detection, and imaging technology. Terahertz systems mainly include pulsed terahertz systems and continuous-wave terahertz systems, the main difference being the form of the terahertz signal. In pulsed terahertz systems, the terahertz signal is a periodic pulse signal in the time domain and a broadband spectrum in the frequency domain, typically covering several THz. These systems usually convert femtosecond laser pulses into terahertz waves using photoconductive antennas, electro-optic crystals, etc. In continuous-wave terahertz systems, the terahertz signal is a periodic continuous signal in the time domain (most commonly a sinusoidal signal), and typically a single frequency point in the frequency domain. Terahertz generation and detection are usually achieved using quantum cascade lasers, electronic frequency conversion, etc. Pulsed terahertz systems typically consist of a terahertz generator, a terahertz detector, an excitation module, and a signal acquisition module. After the terahertz generator generates a terahertz pulse signal under the action of the excitation module, it is transmitted to the terahertz detector through the form of space feed (space radiation) or path feed (transmission line, waveguide). After receiving the terahertz pulse signal, the terahertz detector converts the signal into a current or voltage signal and transmits it to the signal acquisition module.

[0003] However, during terahertz signal transmission, various inherent effects in the terahertz system can disturb the signal of the pulsed terahertz system. These include the Fabry-Perot effect of the terahertz lens in open-feed terahertz transmission, absorption and dispersion of materials in the transmission path, and transmission line processing errors and transmission coupling mismatch in path-feed terahertz transmission. These inherent effects are difficult to eliminate through repeated experiments and can introduce unpredictable distortions into the real signal. Summary of the Invention

[0004] The purpose of this application is to provide a signal correction method for pulsed terahertz systems, in order to solve the problems of high cost of eliminating inherent system effects and easy signal distortion in current pulsed terahertz systems.

[0005] To achieve the above objectives, this application adopts the following technical solution:

[0006] This application provides a signal correction method for pulsed terahertz systems, including:

[0007] The terahertz waveform of the terahertz generator in a pulsed terahertz system is measured using a terahertz waveform standard device. The spectrum F is then calculated by performing a Fourier transform on the time-domain waveform.ref ;

[0008] In a pulsed terahertz system, the internal terahertz detector is used to measure the terahertz signal generated by the terahertz generator. The Fourier transform of the measured terahertz waveform in the time domain is then performed to determine its spectrum F. out ;

[0009] The distortion coefficient D(f) is calculated using the formula: D(f) = (F... out -F ref ) / F ref ;

[0010] When the pulsed terahertz system is a fixed system, only the distortion coefficient needs to be calculated once. Subsequent measurements can directly use the distortion coefficient to correct the terahertz signal. When using the pulsed terahertz system again, the spectrum F1 of the terahertz signal generated by the terahertz generator is measured using its internal terahertz detector. The spectrum of the corrected, distortion-free terahertz signal is then: F real (f)=F1 / (1+D(f)), the corrected terahertz signal spectrum can be obtained by inverse Fourier transform, and then the corrected terahertz time-domain waveform f can be obtained. real (t).

[0011] Based on the above technical solution, this application can achieve the following technical effects:

[0012] After obtaining the spectral data of the terahertz signal using a terahertz waveform standard device, the distortion coefficient is calculated. This distortion coefficient is then used to correct the frequency domain data of the terahertz signal obtained within the terahertz system. Finally, an inverse Fourier transform is performed to obtain the distortion-free terahertz time-domain waveform. This eliminates the need for additional hardware design, resulting in lower costs. Only one calibration of the standard terahertz waveform by sending the terahertz generator in the system to the pulse waveform parameter sub-reference device is required for long-term use. Furthermore, it avoids complex calculations, involving only basic Fourier and inverse Fourier transforms, making it easy to operate. Attached Figure Description

[0013] Figure 1 This is a schematic diagram illustrating the implementation process of a signal correction method for a pulsed terahertz system provided in an embodiment of this application;

[0014] Figure 2 This is a schematic diagram of a signal correction system for a pulsed terahertz system provided in an embodiment of this application;

[0015] Figure 3 This is a system schematic diagram of a specific embodiment of the correction method provided in this application.

[0016] 1-Pulse-type terahertz system; 2-Excitation module; 3-Terahertz generator; 4-Terahertz detector; 5-Signal acquisition module; 6-Terahertz waveform standard device; 11-Pulse-type electro-optic sampling terahertz system; 12-Laser excitation; 13-Electro-optic crystal terahertz generation module; 14-Electro-optic detection module; 15-Signal acquisition module; 16-Pulse waveform parameter sub-reference. Detailed Implementation

[0017] The present application will be further described in detail below with reference to the accompanying drawings and specific embodiments. The advantages and features of the present application will become clearer from the following description and claims. It should be noted that the drawings are all in a very simplified form and are not to scale, and are only used to facilitate and clarify the illustration of the embodiments of the present application.

[0018] It should be noted that, in order to clearly illustrate the content of this application, several embodiments are provided to further explain the different implementations of this application. These embodiments are enumerated rather than exhaustive. Furthermore, for the sake of brevity, content mentioned in the preceding embodiments is often omitted in the following embodiments. Therefore, content not mentioned in the following embodiments can be referred to in the preceding embodiments.

[0019] Example 1

[0020] In pulsed terahertz systems, directly modifying the time-domain waveform of a terahertz signal often introduces complex time-domain signal processing problems. However, the inherent effects of the system are almost constant at each frequency point, reducing complex signal processing in the frequency domain to simple addition and multiplication operations. Therefore, this invention proposes a method to modify the signal by correcting the system's frequency response characteristics, and then converting the modified signal back to the time domain. Figure 1 , 2 As shown in Figure 3, in an embodiment of the present invention, taking the signal correction of a pulsed terahertz system with electro-optic sampling as an example, the steps are as follows:

[0021] Step 1: Use the pulse waveform parameter sub-reference device 16 to measure the terahertz waveform generated by the electro-optic crystal terahertz generation module 13 in the pulsed electro-optic sampling terahertz system 11, and perform a Fourier transform on the time-domain waveform to obtain its spectrum F. ref ;

[0022] The pulse waveform parameter sub-reference device 16 can accurately measure the terahertz time-domain waveform generated by the electro-optic crystal terahertz generation module 13, and the device has a complete traceability chain.

[0023] The pulsed electro-optic sampling terahertz system 11 consists of a laser excitation 12, an electro-optic crystal terahertz generation module 13, an electro-optic detection module 14, and a signal acquisition module 15. Under laser excitation, the electro-optic crystal terahertz generation module 13 loads terahertz information onto the laser through birefringence. The electro-optic detection module 13 then receives the laser and converts it into a current signal related to the terahertz signal. The current signal is input to the signal acquisition module 15, and the terahertz signal can be extracted.

[0024] Step 2: In the pulsed electro-optic sampling terahertz system 11, the electro-optic detection module 14 is used to measure the terahertz signal generated by the electro-optic crystal terahertz generation module 13. The Fourier transform of the measured terahertz waveform in the time domain is then performed to obtain its spectrum F. out ;

[0025] Step 3: Calculate the distortion coefficient D(f), the formula is as follows:

[0026] D(f)=(F out -F ref ) / F ref (1)

[0027] The distortion coefficient is a frequency-dependent function that reflects the degree of distortion of the terahertz signal measured in the pulsed electro-optic sampling terahertz system 11 relative to the standard terahertz time-domain waveform.

[0028] Step 4: When the pulsed electro-optic sampling terahertz system 11 is a fixed system, only the distortion coefficient needs to be calculated once. Subsequent measurements can directly use the distortion coefficient to correct the terahertz signal. When it is necessary to study the effect of the sample on the terahertz signal, the sample is inserted into the transmission path between the electro-optic crystal terahertz generation module 13 and the electro-optic detection module 14. The electro-optic detection module 14 is used to measure the spectrum F1 of the terahertz signal generated by the electro-optic crystal terahertz generation module 13. Then, the spectrum of the corrected, distortion-free terahertz signal is:

[0029] F real (f)=F1 / (1+D(f)) (2)

[0030] The corrected terahertz signal spectrum can then be used to obtain the corrected terahertz time-domain waveform f through inverse Fourier transform. real (t).

[0031] In summary, after obtaining the spectral data of the terahertz signal through a terahertz waveform standard device, the distortion coefficient is calculated. This distortion coefficient is then used to correct the frequency domain data of the terahertz signal obtained within the terahertz system. Finally, an inverse Fourier transform yields the distortion-free terahertz time-domain waveform. This eliminates the need for additional hardware design, resulting in lower costs. Only one calibration of the standard terahertz waveform by sending the terahertz generator in the system to the pulse waveform parameter sub-reference device is required for long-term use. Furthermore, it avoids complex calculations, involving only basic Fourier and inverse Fourier transforms, making it easy to operate.

[0032] The above description is merely an embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of this application should be included within the scope of the claims of this application.

Claims

1. A signal correction method for pulsed terahertz systems, characterized in that, include: The terahertz waveform of the terahertz generator in a pulsed terahertz system is measured using a terahertz waveform standard device. The spectrum F is then calculated by performing a Fourier transform on the time-domain waveform. ref ; In a pulsed terahertz system, the internal terahertz detector is used to measure the terahertz signal generated by the terahertz generator. The Fourier transform of the measured terahertz waveform in the time domain is then performed to determine its spectrum F. out ; The distortion coefficient D(f) is calculated using the formula: D(f) = (F... out -F ref ) / F ref ; When the pulsed terahertz system is a fixed system, only the distortion coefficient needs to be calculated once. Subsequent measurements can directly use the distortion coefficient to correct the terahertz signal. When using the pulsed terahertz system again, the spectrum F1 of the terahertz signal generated by the terahertz generator is measured using its internal terahertz detector. The spectrum of the corrected, distortion-free terahertz signal is then: F real (f)=F1 / (1+D(f)), the corrected terahertz signal spectrum can be obtained by inverse Fourier transform, and then the corrected terahertz time-domain waveform f can be obtained. real (t).

2. The method according to claim 1, characterized in that, The pulse waveform parameter sub-reference device is used to accurately measure the terahertz time-domain waveform generated by the electro-optic crystal terahertz generation module. The device has a complete traceability chain. The pulsed electro-optic sampling terahertz system consists of a laser excitation module, an electro-optic crystal terahertz generation module, an electro-optic detection module, and a signal acquisition module. Under laser excitation, the electro-optic crystal terahertz generation module loads terahertz information onto the laser through birefringence. The electro-optic detection module then receives the laser and converts it into a current signal related to the terahertz signal. The current signal is input to the signal acquisition module, which can then extract the terahertz signal.

3. The method according to claim 1, characterized in that, The distortion coefficient is a frequency-dependent function that reflects the degree of distortion of the terahertz signal measured in the pulsed electro-optic sampling terahertz system relative to the standard terahertz time-domain waveform.

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