Contact type terahertz characteristic parameter test system and test error correction method

Abstract

The invention discloses a contact-type terahertz characteristic parameter test system and a test error correction method, and belongs to the technical field of tests.The test system is based on a 110GHz vector network analyzer, adopts a coaxial waveguide converter for frequency bands below 110GHz, and facilitates system integration; for frequency bands above 110 GHz, 110 GHz signals are used as excitation, the link size of the terahertz module is greatly reduced, the signal quality is remarkably improved, and the terahertz module has the characteristics of large dynamic state, high stability and the like by being matched with a material characteristic testing device, and can realize high signal-to-noise ratio acquisition of original signals; according to the test method provided by the invention, while the test precision is ensured, the operation complexity of the test system is reduced, automatic test of characteristic parameters can be realized, and the test precision can reach + / -1%; the power-adjustable terahertz receiving and transmitting integrated module can meet the test requirements of samples with different attenuation characteristics by adjusting the signal power; by using the terahertz detector, the complexity of a traditional test system is reduced, and the test dynamic state of the system is improved.

Description

Technical Field

[0001] The invention belongs to the field of testing technology, and in particular relates to a contact-type terahertz characteristic parameter testing system and a testing error correction method. Background Art

[0002] The free-space-based terahertz characteristic parameter test method is the preferred method for testing characteristic parameters in the terahertz frequency band. However, the currently commonly used free-space-based terahertz characteristic parameter test method is mainly the non-contact NRW method. The non-contact NRW method has the following main problems: First, the dynamic range is poor, especially in the high-frequency band, and it is impossible to test the characteristic parameters of high-loss materials such as water; second, it has strict requirements on the size of the sample to be tested, and is only suitable for testing large-size (200mm╳200mm) samples, and cannot test small-size (13mm╳13mm) samples; third, it requires precise control of the distance between the material and the antenna, which is difficult. Summary of the invention

[0003] In view of the above technical problems existing in the prior art, the present invention proposes a contact-type terahertz characteristic parameter testing system and a testing error correction method, which are reasonably designed, overcome the shortcomings of the prior art, and have good effects.

[0004] In order to achieve the above object, the present invention adopts the following technical solution:

[0005] A contact terahertz characteristic parameter testing system, which is divided into two modes with 110GHz as the dividing point;

[0006] The frequency bands below 110 GHz include 8 bands: 18-26.5 GHz, 20-33 GHz, 26.5-40 GHz, 33-50 GHz, 40-60 GHz, 50-75 GHz, 60-90 GHz, and 75-110 GHz;

[0007] The frequency bands above 110GHz include 90-140GHz, 110-170GHz, 140-220GHz, 170-260GHz, 260-400GHz, 220-330GHz, 400-600GHz, 600-900GHz, 900-1400GHz, 330-500GHz, 500-750GHz, 750-1100GHz, 1100-1700GHz, and 1400-2200GHz.

[0008] The contact-type terahertz characteristic parameter test system operating in the frequency band below 110 GHz includes a 110 GHz vector network analyzer, a 110 GHz coaxial line, a coaxial waveguide adapter, a material property test device, a control computer, and a display; the 110 GHz coaxial line includes a first 110 GHz coaxial line and a second 110 GHz coaxial line; the coaxial waveguide adapter includes a first coaxial waveguide adapter and a second coaxial waveguide adapter;

[0009] The contact terahertz characteristic parameter test system working in the frequency band above 110GHz includes a 110GHz vector network analyzer, a power module, a radio frequency line, a local oscillator line, a power divider, a test intermediate frequency line, a reference intermediate frequency line, a power adjustable terahertz transceiver integrated module, a terahertz detector, a material property test device, a control computer, and a display; the local oscillator line includes a first local oscillator line and a second local oscillator line; the test intermediate frequency line includes a first test intermediate frequency line and a second test intermediate frequency line;

[0010] A 110 GHz vector network analyzer is configured to provide RF signals and local oscillator signals; and to collect test intermediate frequency and reference intermediate frequency signals;

[0011] 110GHz coaxial line, configured for 110GHz RF, local oscillator, test IF, and reference IF signal transmission;

[0012] A coaxial waveguide adapter is configured to realize signal transmission in a coaxial line and a waveguide;

[0013] A power module, configured to supply power to the power-adjustable terahertz transceiver integrated module and the terahertz detector;

[0014] A radio frequency line is configured to transmit the radio frequency signal output by the vector network analyzer to the frequency multiplication link of the power adjustable terahertz transceiver integrated module as an excitation signal;

[0015] A power divider configured to divide a local oscillator signal of a vector network analyzer into two, namely, a first local oscillator and a second local oscillator;

[0016] A first local oscillator line is configured to transmit a first local oscillator output by the vector network analyzer to a reference link of the power adjustable terahertz transceiver integrated module as an excitation signal;

[0017] A second local oscillator line is configured to transmit a second local oscillator output by the vector network analyzer to a reference link of the terahertz detector as an excitation signal;

[0018] A first test intermediate frequency line is configured to transmit a first test signal of the power-adjustable terahertz transceiver integrated module to a receiving end of the vector network analyzer;

[0019] A second test intermediate frequency line is configured to transmit a second test signal of the terahertz detector to a receiving end of the vector network analyzer;

[0020] A reference intermediate frequency line is configured to transmit a reference signal of the power-adjustable terahertz transceiver integrated module to a receiving end of a vector network analyzer;

[0021] The power-adjustable terahertz transceiver integrated module is configured to generate a terahertz signal to radiate into free space; couple a reference signal; detect the reflected terahertz signal to obtain a first test signal; and adjust the output terahertz signal power according to the signal power requirements of the sample to be tested;

[0022] A terahertz detector is configured to detect a terahertz signal and obtain a second test signal;

[0023] A material property testing device, configured to implement testing of a sample to be tested;

[0024] A control computer configured to control the operation of the vector network analyzer, data acquisition, transmission and processing;

[0025] The display is configured to display the real-time collected signals and test results.

[0026] In addition, the present invention also provides a contact type terahertz characteristic parameter test error correction method, which adopts the contact type terahertz characteristic parameter test system as described above, and comprises the following steps:

[0027] Step 1: Test preparation, set parameters including start frequency, end frequency, frequency multiplication times, RF times, signal power, frequency resolution, etc., start the machine for preheating, and the preheating lasts for 30 minutes;

[0028] Step 2: Reference S 11 Test: Place the short-circuit calibration piece in the material property test device, and use the locking switch of the material property test device to fix the short-circuit calibration piece. After fixing it, use the control software in the control computer to control the vector network analyzer to achieve reference S 11 The signal is tested and saved in the control computer, recorded as α;

[0029] Step 3: Reference S 21 Test: Align the material property test device without gaps and fix it with the locking switch provided by the material property test device. After fixing, use the control software in the control computer to control the vector network analyzer to achieve reference S 21 The signal is tested and saved in the control computer, recorded as β;

[0030] Step 4: Clamp the sample: Place the sample to be tested in the material property testing device, and fix the sample using the locking switch of the material property testing device. After fixing, read the digital caliper data on the material characterization kit as the thickness information of the sample to be tested, and record it in the control software in the control computer;

[0031] Step 5: Sample test: Use the control software in the control computer to control the vector network analyzer to achieve sample S 11 With sample S 21 The signal is tested and saved in the control computer, which are recorded as γκ;

[0032] Step 6: Comparison data: Use the saved α, β, γ, and κ data to solve the comparison data of the sample, that is, A = α / γ, B = β / κ;

[0033] Step 7: Transmission time calculation: Perform inverse Fourier transform on A to obtain time domain data C, search for the time τ corresponding to the second peak of C, select the data of C in the [-τ, τ] time period for Fourier transform, and obtain the time domain filtered data A'; perform inverse Fourier transform on B to obtain time domain data D, select the data of D in the [-τ, τ] time period for Fourier transform, and obtain the time domain filtered data B';

[0034] Step 8: Approximate refractive index calculation: Where a represents the slope of the phase change of B', and c represents the speed of light, which is about 3х10 8 m / s, d is the sample thickness;

[0035] Step 9: Calculation of initial dielectric constant: Let the initial value of loss tangent be 0.05, then the initial value of dielectric constant is expressed as

[0036]

[0037] Step 10: Calculation of reflection coefficient and transmission coefficient: According to the initial dielectric constant, the estimated values ​​of reflection coefficient Γ and transmission coefficient Т are obtained, which are expressed as: The calculated value of the sample comparison data is obtained

[0038] Step 11: Construct error function: Define the following error function, F(ε,ξ)=(B') 2 -(A') 2 -(B") 2 +(A") 2 , where ξ represents the dielectric constant finally solved; thus the dielectric constant solution problem is transformed into the error function calculation problem, and the error threshold is set to 10 -6 ;

[0039] Step 12: Numerical iteration: According to the set error threshold, use the L-BFGS algorithm to perform numerical iteration, and the error is less than 10 -6 The iteration stops when , and the corresponding ξ at this time is the final dielectric constant solved; the test of characteristic parameters including refractive index, loss tangent, absorption coefficient and conductivity is realized.

[0040] Beneficial technical effects brought by the present invention:

[0041] (1) The test system is based on a 110 GHz vector network analyzer. For frequency bands below 110 GHz, a coaxial waveguide converter is used to facilitate system integration. For frequency bands above 110 GHz, a 110 GHz signal is used as the excitation, which greatly reduces the link size of the terahertz module and significantly improves the signal quality. In conjunction with the material property test device, it has the characteristics of large dynamic range and high stability, and can achieve high signal-to-noise ratio acquisition of the original signal.

[0042] (2) The test method provided in the present invention reduces the complexity of the test system operation while ensuring the test accuracy, and can realize the automatic test of characteristic parameters with a test accuracy of up to ±1%;

[0043] (3) The power-adjustable terahertz transceiver module can meet the test requirements of samples with different attenuation characteristics by adjusting the signal power; the use of terahertz detectors reduces the complexity of the traditional test system and improves the test dynamics of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 This is a schematic diagram of a contact-type terahertz characteristic parameter testing system for frequency bands below 110 GHz;

[0045] Figure 2 Schematic diagram of the contact-type terahertz characteristic parameter testing system in the frequency band above 110 GHz;

[0046] Figure 3 The present invention is a flow chart of an error correction method for contact terahertz characteristic parameter testing. DETAILED DESCRIPTION

[0047] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0048] In view of the problems existing in the traditional non-contact NRW method, the present invention discloses a contact terahertz characteristic parameter testing system and a test error correction method.

[0049] Embodiment 1:

[0050] A contact-type terahertz characteristic parameter testing system is divided into two modes with 110 GHz as the dividing point.

[0051] The frequency bands below 110GHz include 8 frequency bands, namely 18-26.5GHz, 20-33GHz, 26.5-40GHz, 33-50GHz, 40-60GHz, 50-75GHz, 60-90GHz, and 75-110GHz; the frequency bands above 110GHz include 14 frequency bands, namely 90-140GHz, 110-170GHz, 140-220GHz, 170-260GHz, 260-400GHz, 220-330GHz, 400-600GHz, 600-900GHz, 900-1400GHz, 330-500GHz, 500-750GHz, 750-1100GHz, 1100-1700GHz, and 1400-2200GHz;

[0052] like Figure 1 As shown, the contact-type terahertz characteristic parameter test system operating in the frequency band below 110 GHz mainly includes a 110 GHz vector network analyzer, a first 110 GHz coaxial line, a second 110 GHz coaxial line, a first coaxial waveguide adapter, a second coaxial waveguide adapter, a material property test device, a control computer, and a display;

[0053] like Figure 2 As shown, the contact terahertz characteristic parameter test system working in the frequency band above 110GHz mainly includes a 110GHz vector network analyzer, a power module, a radio frequency line, a first local oscillator line, a second local oscillator line, a power divider, a first test intermediate frequency line, a second test intermediate frequency line, a reference intermediate frequency line, a power adjustable terahertz transceiver integrated module, a terahertz detector, a material property test device, a control computer, and a display;

[0054] The functions of the 110GHz vector network analyzer are: first, to provide RF signals and local oscillator signals; second, to collect test IF and reference IF signals;

[0055] The 110GHz coaxial line is used for 110GHz RF, local oscillator, test IF, and reference IF signal transmission;

[0056] The coaxial waveguide adapter is used to realize the transmission of signals between the coaxial line and the waveguide;

[0057] The power module is used to supply power to the power-adjustable terahertz transceiver integrated module and the terahertz detector;

[0058] The radio frequency line is used to transmit the radio frequency signal output by the vector network analyzer to the frequency multiplication link of the power adjustable terahertz transceiver integrated module as an excitation signal;

[0059] The power divider is used to split the local oscillator signal of the vector network analyzer into two, namely the first local oscillator and the second local oscillator;

[0060] The first local oscillator line is used to transmit the first local oscillator output by the vector network analyzer to the reference link of the power adjustable terahertz transceiver integrated module as an excitation signal;

[0061] The second local oscillator line is used to transmit the second local oscillator output by the vector network analyzer to the reference link of the terahertz detector as an excitation signal;

[0062] The first test intermediate frequency line is used to transmit the first test signal of the power adjustable terahertz transceiver integrated module to the receiving end of the vector network analyzer;

[0063] The second test intermediate frequency line is used to transmit the second test signal of the terahertz detector to the receiving end of the vector network analyzer;

[0064] The reference intermediate frequency line is used to transmit the reference signal of the power adjustable terahertz transceiver integrated module to the receiving end of the vector network analyzer;

[0065] A first local oscillator line, a second local oscillator line, a power divider, a first test intermediate frequency line, a second test intermediate frequency line, a first reference intermediate frequency line, a second reference intermediate frequency line, a power-adjustable terahertz transceiver integrated module, a terahertz detector, a material property testing device, a control computer, and a display;

[0066] The power-adjustable terahertz transceiver integrated module is used to generate terahertz signals to radiate into free space; second, to couple a reference signal; third, to detect the reflected terahertz signal to obtain a first test signal; and fourth, to adjust the output terahertz signal power according to the signal power requirements of the sample to be tested.

[0067] The terahertz detector is used for terahertz signal detection to obtain a second test signal.

[0068] The material property testing device is used to test the sample to be tested;

[0069] The control computer is used to control the operation of the vector network analyzer, data acquisition, transmission and processing;

[0070] The display is used to display the real-time collected signals and test results.

[0071] Embodiment 2:

[0072] Based on the above embodiment 1, the present invention also provides a contact terahertz characteristic parameter test error correction method, the process of which is as follows: Figure 3 As shown, the specific steps include:

[0073] Step 1: Test preparation, set the start frequency, end frequency, frequency multiplication times, RF times, signal power, frequency resolution and other parameters, start the machine for preheating, and the preheating lasts for 30 minutes;

[0074] Step 2: Reference S 11 Test: Place the short-circuit calibration piece in the material property test device, and use the locking switch of the material property test device to fix the short-circuit calibration piece. After fixing it, use the control software in the control computer to control the vector network analyzer to achieve reference S 11 The signal is tested and saved in the control computer, recorded as α;

[0075] Step 3: Reference S 21 Test: Align the material property test device without gaps and fix it with the locking switch provided by the material property test device. After fixing, use the control software in the control computer to control the vector network analyzer to achieve reference S 21 The signal is tested and saved in the control computer, recorded as β;

[0076] Step 4: Clamp the sample: Place the sample to be tested in the material property testing device, and fix the sample using the locking switch of the material property testing device. After fixing, read the digital caliper data on the material characterization kit as the thickness information of the sample to be tested, and record it in the control software in the control computer;

[0077] Step 5: Sample test: Use the control software in the control computer to control the vector network analyzer to achieve sample S 11 With sample S 21 The signal is tested and saved in the control computer, which are recorded as γκ;

[0078] Step 6: Comparison data: Use the saved αβγκ data to solve the comparison data of the sample, that is, A = α / γ, B = β / κ;

[0079] Step 7: Transmission time calculation: Perform inverse Fourier transform on A to obtain time domain data C, search for the time τ corresponding to the second peak of C, select the data of C in the [-τ, τ] time period for Fourier transform, and obtain the time domain filtered data A'; perform inverse Fourier transform on B to obtain time domain data D, select the data of D in the [-τ, τ] time period for Fourier transform, and obtain the time domain filtered data B';

[0080] Step 8: Approximate refractive index calculation: Where a represents the slope of the phase change of B', and c represents the speed of light, which is about 3х10 8 m / s, d is the sample thickness;

[0081] Step 9: Calculation of initial dielectric constant: Let the initial value of loss tangent be 0.05, then the initial value of dielectric constant can be expressed as

[0082] Step 10: Calculation of reflection coefficient and transmission coefficient: Based on the initial dielectric constant, the estimated values ​​of reflection coefficient Γ and transmission coefficient Т can be obtained, which can be expressed as: This gives the calculated value of the sample comparison data.

[0083]

[0084] Step 11: Construct error function: Define the following error function, F(ε,ξ)=(B') 2 -(A') 2 -(B") 2 +(A") 2 , where ξ represents the dielectric constant finally solved; thus the dielectric constant solution problem is transformed into the error function calculation problem, and the error threshold is set to 10 -6 ;

[0085] Step 12: Numerical iteration: According to the set error threshold, use the L-BFGS algorithm to perform numerical iteration, and the error is less than 10 -6 The iteration stops when , and the corresponding ξ at this time is the final dielectric constant solved; thereby, the test of characteristic parameters such as refractive index, loss tangent, absorption coefficient, and conductivity can be realized.

[0086] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the essential scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A contact-type terahertz characteristic parameter testing system, characterized in that: It is divided into two modes with 110GHz as the dividing point; The frequency bands below 110 GHz include 8 bands: 18-26.5 GHz, 20-33 GHz, 26.5-40 GHz, 33-50 GHz, 40-60 GHz, 50-75 GHz, 60-90 GHz, and 75-110 GHz; The frequency bands above 110GHz include 90-140GHz, 110-170GHz, 140-220GHz, 170-260GHz, 260-400GHz, 220-330GHz, 400-600GHz, 600-900GHz, 900-1400GHz, 330-500GHz, 500-750GHz, 750-1100GHz, 1100-1700GHz, and 1400-2200GHz. The contact-type terahertz characteristic parameter test system operating in the frequency band below 110 GHz includes a 110 GHz vector network analyzer, a 110 GHz coaxial line, a coaxial waveguide adapter, a material property test device, a control computer, and a display; the 110 GHz coaxial line includes a first 110 GHz coaxial line and a second 110 GHz coaxial line; the coaxial waveguide adapter includes a first coaxial waveguide adapter and a second coaxial waveguide adapter; The contact terahertz characteristic parameter test system operating in the frequency band above 110GHz includes a 110GHz vector network analyzer, a power module, a radio frequency line, a local oscillator line, a power divider, a test intermediate frequency line, a reference intermediate frequency line, a power adjustable terahertz transceiver integrated module, a terahertz detector, a material property test device, a control computer, and a display; the local oscillator line includes a first local oscillator line and a second local oscillator line; the test intermediate frequency line includes a first test intermediate frequency line and a second test intermediate frequency line; A 110 GHz vector network analyzer configured to provide a radio frequency signal and a local oscillator signal; Realize the acquisition of test IF and reference IF signals; 110GHz coaxial line, configured for 110GHz RF, local oscillator, test IF, and reference IF signal transmission; A coaxial waveguide adapter is configured to realize signal transmission in a coaxial line and a waveguide; A power module, configured to supply power to the power-adjustable terahertz transceiver integrated module and the terahertz detector; A radio frequency line is configured to transmit the radio frequency signal output by the vector network analyzer to the frequency multiplication link of the power adjustable terahertz transceiver integrated module as an excitation signal; A power divider configured to divide a local oscillator signal of a vector network analyzer into two, namely, a first local oscillator and a second local oscillator; A first local oscillator line is configured to transmit a first local oscillator output by the vector network analyzer to a reference link of the power adjustable terahertz transceiver integrated module as an excitation signal; A second local oscillator line is configured to transmit a second local oscillator output by the vector network analyzer to a reference link of the terahertz detector as an excitation signal; A first test intermediate frequency line is configured to transmit a first test signal of the power-adjustable terahertz transceiver integrated module to a receiving end of the vector network analyzer; A second test intermediate frequency line is configured to transmit a second test signal of the terahertz detector to a receiving end of the vector network analyzer; A reference intermediate frequency line is configured to transmit a reference signal of the power-adjustable terahertz transceiver integrated module to a receiving end of a vector network analyzer; A power-adjustable terahertz transceiver module is configured to generate a terahertz signal and radiate it into free space; Couple one reference signal; Realize detection of reflected terahertz signal to obtain a first test signal; realize adjustment of output terahertz signal power according to the signal power requirement of the sample to be tested; A terahertz detector is configured to detect a terahertz signal and obtain a second test signal; A material property testing device, configured to implement testing of a sample to be tested; A control computer configured to control the operation of the vector network analyzer, data acquisition, transmission and processing; The display is configured to display the real-time collected signals and test results.

2. A contact terahertz characteristic parameter test error correction method, characterized in that: A contact-type terahertz characteristic parameter testing system as claimed in claim 1 comprises the following steps: Step 1: Test preparation, set parameters including start frequency, end frequency, frequency multiplication times, RF times, signal power, frequency resolution, etc., start the machine for preheating, and the preheating lasts for 30 minutes; Step 2: Reference S 11 Test: Place the short-circuit calibration piece in the material property test device, and use the locking switch of the material property test device to fix the short-circuit calibration piece. After fixing it, use the control software in the control computer to control the vector network analyzer to achieve reference S 11 The signal is tested and saved in the control computer, recorded as α; Step 3: Reference S 21 Test: Align the material property test device without gaps and fix it with the locking switch provided by the material property test device. After fixing, use the control software in the control computer to control the vector network analyzer to achieve reference S 21 The signal is tested and saved in the control computer, recorded as β; Step 4: Clamp the sample: Place the sample to be tested in the material property testing device, and fix the sample using the locking switch of the material property testing device. After fixing, read the digital caliper data on the material characterization kit as the thickness information of the sample to be tested, and record it in the control software in the control computer; Step 5: Sample test: Use the control software in the control computer to control the vector network analyzer to achieve sample S 11 With sample S 21 The signal is tested and saved in the control computer, which are recorded as γκ; Step 6: Comparison data: Use the saved α, β, γ, and κ data to solve the comparison data of the sample, that is, A = α / γ, B = β / κ; Step 7: Transmission time calculation: Perform inverse Fourier transform on A to obtain time domain data C, search for the time τ corresponding to the second peak of C, select the data of C in the [-τ, τ] time period for Fourier transform, and obtain the time domain filtered data A'; perform inverse Fourier transform on B to obtain time domain data D, select the data of D in the [-τ, τ] time period for Fourier transform, and obtain the time domain filtered data B'; Step 8: Approximate refractive index calculation: Where a represents the slope of the phase change of B', and c represents the speed of light, which is about 3х10 8 m / s, d is the sample thickness; Step 9: Calculation of initial dielectric constant: Let the initial value of loss tangent be 0.05, then the initial value of dielectric constant is expressed as Step 10: Calculation of reflection coefficient and transmission coefficient: According to the initial dielectric constant, the estimated values ​​of reflection coefficient Γ and transmission coefficient Т are obtained, which are expressed as: The calculated value of the sample comparison data is obtained Step 11: Construct error function: Define the following error function, F(ε,ξ)=(B') 2 -(A') 2 -(B") 2 +(A") 2 , where ξ represents the dielectric constant finally solved; thus the dielectric constant solution problem is transformed into an error function calculation problem, and the error threshold is set to 10 -6 ; Step 12: Numerical iteration: According to the set error threshold, use the L-BFGS algorithm to perform numerical iteration, and the error is less than 10 -6 The iteration stops when , and the corresponding ξ at this time is the final dielectric constant solved; the test of characteristic parameters including refractive index, loss tangent, absorption coefficient and conductivity is realized.

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