CN115096442A - Terahertz superconducting array detector characteristic measuring device and measuring method - Google Patents
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Abstract
The novel terahertz superconducting array detector characteristic measuring device and the measuring method provided by the invention have the advantages that the switching of the microwave switch is mainly controlled through the electric signal, the measuring device is in different measuring states, the integration method of the measuring system is completed through the same system link, and the corresponding function is completed through the method of the rear-end automatic calibration program. The measuring device and the measuring method of the invention can realize that: the method has the advantages of measuring noise reading of the KIDs detector, measuring unbalance degree correction parameters of the reading circuit system and reading S21 parameters of the KIDs detector, being easy to implement, reducing unnecessary operation of the system, improving stability of the system and effectively reducing measurement errors.
Description
Technical Field
The invention relates to a terahertz detector and a frequency response measuring method of a reading circuit system, and belongs to the field of terahertz technology research.
Background
A superconducting dynamic Inductance detector (KIDs) is a novel low-temperature high-sensitivity detector and can be used for target imaging observation from millimeter waves to terahertz, optics/ultraviolet rays, X rays and gamma frequency bands.
According to the KIDs working principle, when an external radio frequency signal irradiates the KIDs detector, the receiver generates a phenomenon of superconducting Cooper pair rupture after receiving photon energy, so that the dynamic resistance and dynamic inductance of the microwave resonator are changed, and the characteristics (Q factor, amplitude, phase and the like) of the microwave resonator are changed. The information characteristic of the incident photon signal can be indirectly detected by acquiring the amplitude (which can be characterized by the S21 parameter) or phase change information of the microwave resonator through a reading circuit. Since the microwave resonator of the KIDs detector can realize a high Q value design more than 104, the possibility of coupling a plurality (>1000) of KIDs detectors with different resonant frequencies on a single transmission line is made possible. If a comb signal generator is adopted to add excitation signals corresponding to the resonant frequencies of the KIDs detector array units on a transmission line, all output signals of the KIDs detector array can be read simultaneously through a frequency division multiplexing FDM (frequency division multiplexing) technology.
The phase noise is one of the main parameters for characterizing the performance of the KIDs detector and further directly influencing the overall sensitivity of the terahertz imaging system, and the importance of the phase noise is needless to say. At present, a KIDs phase noise measurement hardware system generally adopts a microwave quadrature mixer, and combines auxiliary circuit modules such as a low noise amplifier, a power divider, an adjustable attenuator, a fixed attenuator, a band-pass filter, a low-pass filter and the like to realize the measurement of phase noise in a Homodyne mixing (Homodyne) mode. The phase noise theta (f) and the amplitude noise A (f) of the KIDs detector can be obtained simultaneously by processing data of I, Q two paths of orthogonal intermediate frequency output signals, and the calculation formula can be as follows:
θ(f)＝FFT(tan -1 (I(t)/Q(t))) (2)
both theoretical and measured results confirm that phase noise dominates both types of noise, typically on the order of one to two orders of magnitude higher than amplitude noise. The general principle of the broadband quadrature mixer mainly comprises two double-balanced mixers, a 3dB equiphase power divider and a 3dB equiphase directional coupler with an orthogonal (90 DEG) phase difference. After the radio frequency signal with equal phase and the local oscillator signal with 90-degree phase difference are respectively subjected to down-mixing in the two double-balanced mixers, two paths of intermediate frequency signals I and Q with orthogonal phase difference are output.
The existing KIDs sensing circuit has the following problems:
1) because the existing circuit design method and processing technology are difficult to realize a power divider and a directional coupler with perfect equal power division, 90-degree phase difference and high isolation in a broadband, the two orthogonal intermediate frequency output ends I, Q of the orthogonal mixer microwave generally have the phenomenon of unbalanced amplitude and phase, and the specific numerical value changes along with the frequency. This makes the calibration of the quadrature mixer a cumbersome and demanding process in phase noise measurements on superconducting KIDs detectors.
2) Meanwhile, as described above, the information characteristic of the incident photon signal can be indirectly detected by acquiring the amplitude (which can be characterized by the S21 parameter) of the microwave resonator through the readout circuit. It takes a lot of time to acquire the KIDs resonator amplitude using ADC sampling and software processing of computer data, so a vector network analyzer is often used to scan the S21 parameter of the resonator quickly. However, in the existing scheme, an amplifying circuit is needed for measuring the S21 parameter of the resonator by using a vector network analyzer, two sets of circuit systems need to be switched back and forth in the noise reading and S21 parameter acquisition testing processes, the instability of the system is increased, and the complexity of operation is increased.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a device and a method for measuring the characteristics of a terahertz superconducting array detector, so as to overcome the defects of the prior art.
The technical scheme provided by the invention is as follows:
the utility model provides a terahertz is superconductive array detector characteristic measuring device now, includes frequency signal source, clock signal synchronizer, vector network analysis appearance, reading circuit system, ADC data acquisition module, control computer and the refrigerator of installation KIDs detector which characterized in that:
the readout circuitry comprises a directional coupler, a microwave switch a, a microwave switch B, and a mixer, wherein:
the signal input end of the directional coupler is connected with the frequency signal source, and the two signal output ends of the directional coupler are respectively connected with the microwave switch A and the local oscillator signal input end of the frequency mixer;
a signal input end of the microwave switch A is provided with a first channel switch contact and a second channel switch contact, the first channel switch contact is connected with the directional coupler, the second channel switch contact is connected with one port of the vector network analyzer, and a signal output end of the microwave switch A is connected with a signal input end of the KIDs detector;
the signal output end of the microwave switch B is provided with a first channel switch contact and a second channel switch contact, the signal input end of the microwave switch B is connected with the signal output end of the KIDs detector, the first channel switch contact of the microwave switch B is connected with the resonance signal input end of the mixer, and the second channel switch contact of the microwave switch B is connected with two ports of the vector network analyzer;
two orthogonal intermediate frequency output ends I, Q of the frequency mixer are respectively connected with the ADC data acquisition module;
the ADC data acquisition module is connected with the control computer, and is used for uploading data to the control computer and receiving a control instruction of the control computer;
the control signal input ends of the frequency signal source, the vector network analyzer, the microwave switch A and the microwave switch B are respectively connected with the control computer, and the control computer controls the operation mode of the control computer according to instructions input by a user or preloaded programs.
On the basis of the above scheme, a preferable scheme further includes:
further, the signal output end of the microwave switch A is connected with the signal input end of the KIDs detector through a first attenuator, a first DC-blocking device and a second attenuator which are sequentially connected in series; the signal output end of the KIDs detector is connected with the signal input end of the microwave switch through a low-temperature amplifier, a third attenuator, a first normal-temperature amplifier, a fourth attenuator and a second normal-temperature amplifier which are sequentially connected in series; the output end I of the frequency mixer is connected with the ADC data acquisition module through a fifth attenuator and a low-pass filter, and the output end Q of the frequency mixer is connected with the ADC data acquisition module through a sixth attenuator and a low-pass filter; a third DC isolator is arranged between the directional coupler and the mixer;
in the assembly, the second attenuator, the low-temperature amplifier and the KIDs detector are arranged in a cold chamber of the refrigerator together; the first attenuator, the fourth attenuator, the fifth attenuator and the sixth attenuator are all adjustable attenuators, and the first normal-temperature amplifier and the second normal-temperature amplifier are all low-noise amplifiers;
the first attenuator is used for adjusting the input power of the KIDs detector and preventing the detector from power saturation;
the fourth attenuator is used for adjusting the power of the resonant port of the mixer input by the amplifier and ensuring that the dynamic range of the KIDs detector is consistent with the RF dynamic range of the mixer;
the fifth attenuator and the sixth attenuator are used for adjusting the amplitude imbalance of the two paths of output signals of the mixer I, Q.
Furthermore, the first attenuator is an adjustable attenuator with 0-60 dB, the second attenuator is a 30dB attenuator, the third attenuator is a 3dB attenuator, the fourth attenuator is an adjustable attenuator with 0-30 dB, and the fifth attenuator and the sixth attenuator are step attenuators with the step of 0.1 dB.
Further, the microwave switch a and the microwave switch B are single-pole double-throw microwave switches.
A measuring method based on the terahertz superconducting array detector characteristic measuring device is characterized by comprising the following steps:
s1, measuring correction parameters of system unbalance
Setting a resonant frequency to be detected, installing a KIDs detector sample with the resonant frequency in the refrigerator, and connecting the frequency signal source and the vector network analyzer into a synchronous clock signal to synchronize signals output by the frequency signal source and the vector network analyzer;
taking a signal output by the frequency signal source as a test signal, wherein the frequency of the test signal is the same as the resonant frequency of a KIDs detector sample, taking a signal output by one port of a vector network analyzer as a calibration signal, and controlling the frequency difference value of the calibration signal and the test signal within a preset range;
connecting a second channel switch contact of the microwave switch A with a signal output end of the microwave switch A, connecting a signal input end of the microwave switch B with a first channel switch contact of the microwave switch B, and establishing a calibration link;
acquiring a correction parameter of the unbalance degree of the reading circuit system under the resonance frequency according to a sampling value of an ADC data acquisition module, and calibrating the reading circuit system based on the correction parameter;
s21 parameter measurement of KIDs detector
Installing a KIDs detector to be detected in the refrigerator, connecting a second channel switch contact of the microwave switch A with a signal output end of the microwave switch A, connecting a signal input end of the microwave switch B with a second channel switch contact of the microwave switch B, selecting and measuring an S21 parameter in a vector network analyzer, and measuring the resonance characteristic of the KIDs detector;
s3. noise readout of KIDs Detector
Installing a KIDs detector to be detected in the refrigerator, connecting a first channel switch contact of a microwave switch A with a signal output end of the microwave switch A, connecting a signal input end of a microwave switch B with the first channel switch contact of the microwave switch B, establishing a homodyne frequency detection circuit, reading an output signal by using a calibrated reading circuit system, and sampling data by using an ADC data acquisition module.
On the basis of the above scheme, a preferable scheme further includes:
further, in step S1, the difference between the frequencies of the calibration signal and the test signal is between 1 kHz and 10 kHz.
Further, in step S1, the process of obtaining the correction parameter of the imbalance degree of the readout circuit system at the resonant frequency according to the sampling value of the ADC data acquisition module is as follows:
drawing a relation curve of signal values of an output end I and an output end Q of the mixer by using a sampling value of a discrete ADC data acquisition module, naming the relation curve as an IQ circle, and expressing the IQ circle by the following equation:
I＝I 0 +A I cosγ
Q＝Q 0 +A Q sinγ
wherein, I 0 And Q 0 Denotes the offset of the I and Q channel outputs, A I And A Q Representing the degree of imbalance of the I and Q channel signal amplitudes, and gamma representing a fixed initial phase difference;
said I 0 、Q 0 、A I 、A Q And gamma is the correction parameter to be solved, and the IQ circle is fitted by using a least square method to solve the correction parameter.
Further, in step S3, the method for calibrating the readout circuitry includes:
the signal amplitude is adjusted by an adjustable attenuator arranged between the output end of the mixer and the ADC data acquisition module.
Has the advantages that:
1) the device and the method for measuring the characteristics of the terahertz superconducting array detector have the functions of reading out noise of a KIDs detector, measuring correction parameters of system unbalance, reading out S21 parameters of the KIDs detector and the like;
2) the measuring device and the measuring method can change the corresponding link by controlling the switching control of the computer on the microwave switch, thereby reducing unnecessary operation of the system and improving the stability of the system;
3) the measuring device and the measuring method system accurately acquire the resonant frequency and the S21 characteristic of a KIDs detector array by utilizing the measuring function of the vector network analyzer, which is the basic measurement of the subsequent KIDs noise characteristic or sensitivity characterization, and simultaneously provide a synchronous signal source for the homodyne mixer circuit through the vector network analyzer, which is used for the non-equilibrium calibration of the homodyne mixer circuit, and can effectively reduce the measuring error under the same system. Compared with the traditional measuring method, the method can control the resonance depth of the KIDs detector test signal within the measuring range of the vector network analyzer by adjusting the adjustable attenuator, and is simple and convenient to operate.
Drawings
FIG. 1 is a system schematic of a measuring device of the present invention;
FIG. 2 is a block diagram of a ADC data processing module;
FIG. 3 is a schematic diagram of an embodiment of an IQ circle before correction;
FIG. 4 is a schematic diagram of the corrected IQ circle.
Detailed Description
The present invention will now be described in further detail with reference to the accompanying drawings.
As shown in fig. 1, a characteristic measurement device for a terahertz superconducting array detector includes a frequency signal source, a clock signal synchronization device, a vector network analyzer, a readout circuit system, an ADC data acquisition module, a control computer, and a refrigerator equipped with a KIDs detector.
The readout circuitry comprises a directional coupler, a microwave switch a, a microwave switch B, and a mixer, wherein:
the signal input end of the directional coupler is connected with a frequency signal source, and two signal output ends of the directional coupler are respectively connected with the microwave switch A and a local oscillator signal input end (LO) of the frequency mixer;
a signal input end of the microwave switch A is provided with a first channel switch contact and a second channel switch contact, the first channel switch contact is connected with the directional coupler, the second channel switch contact is connected with a Port (Port1) of the vector network analyzer, and a signal output end of the microwave switch A is connected with a signal input end of the KIDs detector;
a signal output end of the microwave switch B is provided with a first channel switch contact and a second channel switch contact, a signal input end of the first channel switch contact is connected with a signal output end of the KIDs detector, a first channel switch contact of the microwave switch B is connected with a resonance signal input end (RF) of the frequency mixer, and a second channel switch contact of the microwave switch B is connected with a second Port (Port2) of the vector network analyzer;
and two orthogonal intermediate frequency output ends I, Q of the frequency mixer are respectively connected with terminals of two signal acquisition channels of the ADC data acquisition module.
The ADC data acquisition module is connected with the control computer, and uploads data to the control computer and receives a control instruction of the control computer.
The control signal input ends of the frequency signal source, the vector network analyzer, the microwave switch A and the microwave switch B are respectively connected with the control computer, and the control computer controls the operation according to instructions input by a user or preloaded programs, including switching control of the microwave switch, regulation of the working modes of the frequency signal source and the vector network analyzer and the like.
The signal output end of the microwave switch A is connected with the signal input end of the KIDs detector through a first attenuator, a first DC-blocking device and a second attenuator which are sequentially connected in series; the signal output end of the KIDs detector is connected with the signal input end of the microwave switch through a low-temperature amplifier, a third attenuator, a first normal-temperature amplifier, a fourth attenuator and a second normal-temperature amplifier which are sequentially connected in series; the output end I of the frequency mixer is connected with the ADC data acquisition module through a fifth attenuator and a low-pass filter, and the output end Q of the frequency mixer is connected with the ADC data acquisition module through a sixth attenuator and a low-pass filter; and a third DC isolator is arranged between the directional coupler and the frequency mixer.
Wherein:
the second attenuator, the low-temperature amplifier and the KIDs detector are arranged in a cold bin of the refrigerator together; the first attenuator, the fourth attenuator, the fifth attenuator and the sixth attenuator are all adjustable attenuators, and the first normal-temperature amplifier and the second normal-temperature amplifier are all low-noise amplifiers.
The first attenuator is used for adjusting the input power of the KIDs detector and preventing the detector from power saturation;
the fourth attenuator is used for adjusting the power of the resonant port of the mixer input by the amplifier and ensuring that the dynamic range of the KIDs detector is consistent with the RF dynamic range of the mixer;
the fifth attenuator and the sixth attenuator are used for adjusting the amplitude imbalance of the two paths of output signals of the mixer I, Q.
In a preferred embodiment, in the present embodiment, the first attenuator is an adjustable attenuator with a step size of 0.1dB, the second attenuator is an attenuator with a step size of 30dB, the third attenuator is a 3dB attenuator, the fourth attenuator is an adjustable attenuator with a step size of 0-30 dB, and the fifth and sixth attenuators are step (adjustable) attenuators with a step size of 0.1 dB. The microwave switch A and the microwave switch B adopt single-pole double-throw microwave switches.
The working principle and the measuring method of the terahertz superconducting array detector characteristic measuring device are as follows.
(1) Noise readout of KIDs detector
And installing a KIDs detector to be detected in the refrigerator, connecting a first channel switch contact of the microwave switch A with a signal output end of the microwave switch A, connecting a signal input end of the microwave switch B with a first channel switch contact of the microwave switch B, and establishing a zero-difference frequency detection circuit.
In the circuit, a Frequency signal source outputs a detection signal, the detection signal is divided into two channels by a directional coupler, one is used as a Local-Oscillator (LO) signal of an I-Q mixer, and the other is used as a Radio Frequency (RF) signal of the Local-Oscillator signal and is output after modulation and multi-stage amplification by a KID detector. Two paths of signals are simultaneously used as input signals of an I-Q mixer, the signals are output as direct current signals through the difference frequency of the mixer, two paths of time domain direct current signals are filtered by a step attenuator (impedance converter) and a Low Pass Filter (LPF) and then input to an ADC sampling module, the ADC sampling module preferably adopts a high-precision data sampling card, and the sampling values are I (t) and Q (t) respectively. And finally, converting the two paths of time domain signals into amplitude or phase noise of a frequency domain through Fourier transform. The frequency signal source generates the frequency of the resonant point of the KIDs detector, and different input powers can be set for convenient measurement.
And the signal generated by the frequency signal source is divided into two paths of signals with the same frequency through the directional coupler. The direct-through end of the directional coupler filters out direct-current signals through a direct-current blocking device and then enters a local oscillation input port of the frequency mixer; after the coupling end of the directional coupler outputs another path of signal, the signal passes through an adjustable attenuator to adjust the signal intensity of the signal entering the detector (the saturation power of a KIDs detector is lower and is generally lower than-60 dBm), then the signal passes through the KIDs detector in a low-temperature environment, passes through a low-temperature amplifier HEMT and a multi-stage normal-temperature amplifier, and then the signal enters the adjustable attenuator (the amplitude of the signal is adjusted to adapt to the dynamic range of the radio frequency of the mixer); after the signal is output from the adjustable attenuator, the signal enters an IQ mixer; i, Q signals output by the IQ mixer pass through an adjustable attenuator (amplitude imbalance of IQ two paths) and a low-pass filter of the next stage respectively, enter an ADC data acquisition module to sample data, and are processed by a software algorithm to calculate the amplitude and phase noise of the detector.
(2) Calibration parameter measurement of system imbalance
KIDs detectors tend to have high sensitivity and large dynamic range, which depends not only on the detector itself but also on its readout circuitry. In a KID detector homodyne mixing reading system, an I-Q mixer often has the defect of unbalanced two paths of outputs. This not only limits the dynamic range of the entire readout system, but also makes the data acquisition inaccurate and affects the measurement of noise, thus requiring calibration of the imbalance of the readout circuitry.
The calibration process comprises the following steps:
setting a resonant frequency to be detected, installing a KIDs detector sample with the resonant frequency in the refrigerator, and connecting the frequency signal source and the vector network analyzer into a synchronous clock signal to synchronize signals output by the frequency signal source and the vector network analyzer;
taking a signal output by the frequency signal source as a test signal, wherein the frequency of the test signal is the same as the resonant frequency of a KIDs detector sample, taking a signal output by one port of a vector network analyzer as a calibration signal, and controlling the frequency difference value of the calibration signal and the test signal within a preset range;
connecting a second channel switch contact II of the microwave switch A with a signal output end of the microwave switch A, connecting a signal input end of the microwave switch B with a first channel switch contact I of the microwave switch B, and establishing a calibration link;
according to ADC data acquisition module sampling value, obtain under this resonant frequency correction parameter of reading out circuit system unbalance degree, specifically do:
drawing a relation curve of signal values of an output end I and an output end Q of the mixer by using a sampling value of a discrete ADC data acquisition module, naming the relation curve as an IQ circle, and expressing the IQ circle by the following equation:
I＝I 0 +A I cosγ
Q＝Q 0 +A Q sinγ
wherein, I 0 And Q 0 (center of ellipse) represents the offset of the I and Q channel outputs, respectively, A I And A Q (major axis of ellipse and minor axis thereof) represents the degree of imbalance of the I and Q channel signal amplitudes, γ (inclination angle of ellipse) represents a fixed initial phase difference;
said I 0 、Q 0 、A I 、A Q Gamma is the correction parameter to be solved, thenAnd fitting the IQ circle by using a least square method to obtain the correction parameters.
And finally, based on the correction parameters, adjusting the amplitude of the reading circuit system through a rear-end 0.1dB step attenuator, performing phase correction through software, and sorting out the image of the IQ circle in real time, thereby facilitating observation and data processing. As shown in fig. 3 and 4, before the calibration, the IQ circle is elliptical, and the calibrated IQ circle is a standard perfect circle (IQ has the same amplitude and a phase difference of 90 °).
In the prior art, the system needs to disassemble the whole system to test the unbalance parameters of the corresponding frequency points, the operation is complicated and troublesome, the stability of the system is increased, and the system structure is influenced to a certain extent. The invention designs the single-pole double-throw microwave switch, and adopts an electric signal control method to switch the corresponding access, thereby reducing the unnecessary operation of the system.
In the above process of the method of the invention, when the signal source is set, the difference between the frequency of the signal output to one port of the vector network analyzer and the resonant frequency of the KIDs detector sample is several kHz, theoretically within 100kHz, the smaller the difference between the two frequencies is, the better the difference is, but the IQ circle is not easily obtained by the undersize difference, so the frequency difference can be generally controlled to be several kHz, for example, 1-10 kHz. The signal generated by the frequency signal source enters an LO (local oscillator) port of the IQ mixer through a straight-through end; signals generated by the vector network analyzer enter a 0-60 dB adjustable attenuator and a DC-isolator through the switching of a microwave switch, are connected with a 3dB attenuator, a low noise amplifier, a 0-30 dB adjustable attenuator and a secondary low noise amplifier, and then enter an RF (radio frequency) port of an IQ mixer through the switching of the microwave switch; the mixer samples IQ two-path signals after mixing processing of the two paths of signals through an ADC, and therefore correction parameters of the unbalance degree of a reading circuit system at the working resonance point of the KIDs detector are obtained.
(3) Measurement of S21 parameter of KIDs detector
And installing a KIDs detector to be detected in the refrigerator, connecting a second channel switch contact of the microwave switch A with a signal output end of the microwave switch A, connecting a signal input end of the microwave switch B with a second channel switch contact of the microwave switch B, selecting and measuring an S21 parameter in a vector network analyzer, and measuring the resonance characteristic of the KIDs detector.
The KIDs detector detects signals with high sensitivity by detecting the characteristics that the resonance frequency of the resonator is changed by the signals and the amplitude of the resonance curve of the resonance becomes shallow and widened, so that the S21 parameter of the detector can well represent the detection characteristics of the detector. In the embodiment, after a signal generated by a Port (Port1) of a vector network analyzer is switched by a single-pole double-throw microwave switch A, the signal enters a 0-60 dB adjustable attenuator and a DC blocking device, is connected with a 3dB attenuator, a low-noise amplifier, a 0-30 dB adjustable attenuator and a secondary low-noise amplifier through a low-temperature test system, and then is switched by a microwave switch B to enter an RF (radio frequency) Port of an IQ mixer; after passing through the low-temperature test system, the signal passes through the normal-temperature amplifier and then is connected to a two-Port (Port2) of the vector network analyzer, so that the S21 parameter of the detector is measured.
The measuring device integrates the measuring function of a vector network analyzer, can accurately acquire the resonant frequency and S21 of the KIDs array, and is basic measurement data of noise characteristics or sensitivity representation of a follow-up KIDs array pixel detector; a vector network analyzer provides a synchronous signal source for the homodyne mixing circuit, and the synchronous signal source is used for the non-equilibrium calibration of the homodyne mixing circuit. Meanwhile, compared with the traditional measuring method, the scheme can ensure that the resonance depth of the test signal of the KIDs detector is within the measuring range of the vector network analyzer (the measuring range of the vector network analyzer is generally-40 dBm-10 dBm) by adjusting the attenuation of the two adjustable attenuators.
The above are only preferred embodiments of the present invention, and the scope of the present invention is not limited to the above examples, and all technical solutions that fall under the spirit of the present invention belong to the scope of the present invention. It should be noted that modifications and embellishments within the scope of the invention may be made by those skilled in the art without departing from the principle of the invention.
Claims (8)
1. The utility model provides a terahertz superconduction array detector characteristic measuring device, includes frequency signal source, clock signal synchronizer, vector network analysis appearance, reads out circuit system, ADC data acquisition module, control computer and the refrigerator of installation KIDs detector which characterized in that:
the readout circuitry comprises a directional coupler, a microwave switch a, a microwave switch B, and a mixer, wherein:
the signal input end of the directional coupler is connected with the frequency signal source, and the two signal output ends of the directional coupler are respectively connected with the microwave switch A and the local oscillator signal input end of the frequency mixer;
a signal input end of the microwave switch A is provided with a first channel switch contact and a second channel switch contact, the first channel switch contact is connected with the directional coupler, the second channel switch contact is connected with one port of the vector network analyzer, and a signal output end of the microwave switch A is connected with a signal input end of the KIDs detector;
the signal output end of the microwave switch B is provided with a first channel switch contact and a second channel switch contact, the signal input end of the microwave switch B is connected with the signal output end of the KIDs detector, the first channel switch contact of the microwave switch B is connected with the resonance signal input end of the mixer, and the second channel switch contact of the microwave switch B is connected with two ports of the vector network analyzer;
two orthogonal intermediate frequency output ends I, Q of the frequency mixer are respectively connected with the ADC data acquisition module;
the ADC data acquisition module is connected with the control computer, and is used for uploading data to the control computer and receiving a control instruction of the control computer;
the control signal input ends of the frequency signal source, the vector network analyzer, the microwave switch A and the microwave switch B are respectively connected with the control computer, and the control computer controls the operation mode of the control computer according to instructions input by a user or preloaded programs.
2. The terahertz superconducting array detector characteristic measuring device according to claim 1, wherein:
the signal output end of the microwave switch A is connected with the signal input end of the KIDs detector through a first attenuator, a first DC-blocking device and a second attenuator which are sequentially connected in series; the signal output end of the KIDs detector is connected with the signal input end of the microwave switch through a low-temperature amplifier, a third attenuator, a first normal-temperature amplifier, a fourth attenuator and a second normal-temperature amplifier which are sequentially connected in series; the output end I of the frequency mixer is connected with the ADC data acquisition module through a fifth attenuator and a low-pass filter, and the output end Q of the frequency mixer is connected with the ADC data acquisition module through a sixth attenuator and a low-pass filter; a third DC isolator is arranged between the directional coupler and the mixer;
in the assembly, the second attenuator, the low-temperature amplifier and the KIDs detector are arranged in a cold chamber of the refrigerator together; the first attenuator, the fourth attenuator, the fifth attenuator and the sixth attenuator are all adjustable attenuators, and the first normal-temperature amplifier and the second normal-temperature amplifier are all low-noise amplifiers;
the first attenuator is used for adjusting the input power of the KIDs detector and preventing the detector from power saturation;
the fourth attenuator is used for adjusting the power of the resonant port of the mixer input by the amplifier and ensuring that the dynamic range of the KIDs detector is consistent with the RF dynamic range of the mixer;
the fifth attenuator and the sixth attenuator are used for adjusting the amplitude imbalance of the two paths of output signals of the mixer I, Q.
3. The terahertz superconducting array detector characteristic measuring device according to claim 2, wherein:
the first attenuator is an adjustable attenuator of 0-60 dB, the second attenuator is an attenuator of 30dB, the third attenuator is an attenuator of 3dB, the fourth attenuator is an adjustable attenuator of 0-30 dB, and the fifth attenuator and the sixth attenuator are step attenuators with steps of 0.1 dB.
4. The terahertz superconducting array detector characteristic measuring device according to claim 1, wherein:
the microwave switch A and the microwave switch B are single-pole double-throw microwave switches.
5. A measuring method based on the terahertz superconducting array detector characteristic measuring device as claimed in any one of claims 1 to 4, characterized by comprising the following steps:
s1, measuring correction parameters of system unbalance
Setting a resonant frequency to be detected, installing a KIDs detector sample with the resonant frequency in the refrigerator, and connecting the frequency signal source and the vector network analyzer into a synchronous clock signal to synchronize signals output by the frequency signal source and the vector network analyzer;
taking a signal output by the frequency signal source as a test signal, wherein the frequency of the test signal is the same as the resonant frequency of a KIDs detector sample, taking a signal output by a port of a vector network analyzer as a calibration signal, and controlling the frequency difference value of the calibration signal and the test signal within a preset range;
connecting a second channel switch contact of the microwave switch A with a signal output end of the microwave switch A, connecting a signal input end of the microwave switch B with a first channel switch contact of the microwave switch B, and establishing a calibration link;
acquiring a correction parameter of the unbalance degree of the readout circuit system under the resonant frequency according to a sampling value of an ADC data acquisition module, and calibrating the readout circuit system based on the correction parameter;
s21 parameter measurement of KIDs detector
Installing a KIDs detector to be detected in the refrigerator, connecting a second channel switch contact of the microwave switch A with a signal output end of the microwave switch A, connecting a signal input end of the microwave switch B with a second channel switch contact of the microwave switch B, selecting and measuring an S21 parameter in a vector network analyzer, and measuring the resonance characteristic of the KIDs detector;
s3. noise readout of KIDs Detector
Installing a KIDs detector to be detected in the refrigerator, connecting a first channel switch contact of a microwave switch A with a signal output end of the microwave switch A, connecting a signal input end of a microwave switch B with the first channel switch contact of the microwave switch B, establishing a homodyne frequency detection circuit, reading an output signal by using a calibrated reading circuit system, and sampling data by using an ADC data acquisition module.
6. The method for measuring according to claim 5, wherein in step S1, the difference between the frequencies of the calibration signal and the test signal is between 1 kHz and 10 kHz.
7. The measurement method according to any one of claims 4 to 6, wherein in step S1, the process of obtaining the correction parameter of the imbalance degree of the readout circuit system at the resonant frequency according to the sampling value of the ADC data acquisition module is:
drawing a relation curve of signal values of an output end I and an output end Q of the mixer by using a sampling value of a discrete ADC data acquisition module, naming the relation curve as an IQ circle, and expressing the IQ circle by the following equation:
I＝I 0 +A I cosγ
Q＝Q 0 +A Q sinγ
wherein, I 0 And Q 0 Denotes the offset of the I and Q channel outputs, A I And A Q Representing the degree of imbalance of the I and Q channel signal amplitudes, and gamma representing a fixed initial phase difference;
said I 0 、Q 0 、A I 、A Q And gamma is the correction parameter to be solved, and the IQ circle is fitted by using a least square method to solve the correction parameter.
8. The measurement method according to claim 7, wherein in step S3, the method for calibrating the readout circuitry comprises:
the signal amplitude is adjusted by an adjustable attenuator arranged between the mixer output and the ADC data acquisition module.
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