CN109470936B - KIDs detector noise test circuit and test method based on active quadrature mixer - Google Patents
KIDs detector noise test circuit and test method based on active quadrature mixer Download PDFInfo
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Abstract
The invention provides a KIDs detector noise test circuit and a test method based on an active quadrature mixer, and the test circuit is characterized by comprising a frequency synthesis source, a directional coupler, a KIDs detector reading circuit module, an adjustable phase shifter, an active mixing circuit module, a filter circuit module, a data acquisition card, a control computer and the like. The testing circuit takes a broadband Gilbert double-balanced active orthogonal mixing circuit structure as a core module, can complete noise testing work on KIDs detector chips, has very excellent amplitude/phase balance degree and port isolation degree, has weak parasitic direct current bias voltage generated by a frequency output port, is accurate in measurement, does not need to calibrate a mixer independently, simplifies the measuring process, and reduces the power level of a frequency comprehensive source.
Description
Technical Field
The invention relates to a KIDs detector noise test circuit and a test method based on an active quadrature mixer, and belongs to the field of terahertz/optical 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, optical/ultraviolet, 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 obtaining the (amplitude or phase) change information of the microwave resonator through a reading circuit. Microwave resonator can achieve more than 10 due to KIDs detector4The high Q design makes it possible to couple multiple(s) onto a single transmission line>1000) KIDs detectors with different resonant frequencies are 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) technology.
Noise, especially phase noise, is one of the main parameters characterizing the performance of KIDs detectors and computing system sensitivity. At present, a general KIDs noise measurement hardware system generally adopts a microwave passive quadrature mixer, 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, realizes noise measurement in a Homodyne mixing (Homodyne) mode, and processes data of two paths of quadrature intermediate frequency output signals to obtain phase noise and amplitude noise at the same time. However, the two quadrature intermediate frequency outputs of the passive quadrature mixer generally have amplitude and phase imbalance phenomena, and the specific value varies with the frequency, which makes the calibration of the quadrature mixer a complicated and demanding process. In addition, microwave passive quadrature mixers require large local oscillator excitation levels. On one hand, the method puts higher requirements on the output power level of the frequency synthesis source, and on the other hand, the intermediate frequency output end has parasitic larger direct current bias voltage, so that the direct current amplification multiple and the dynamic range of the analog-digital conversion sampling circuit are limited.
Disclosure of Invention
Based on the defects of the prior art, the invention provides a KIDs detector noise test circuit and a test method based on an active quadrature mixer, which can improve the defects of the prior art.
The technical scheme provided by the invention for realizing the aim is as follows:
a KIDs detector noise test circuit based on active quadrature mixer is characterized by comprising a frequency synthesis source, a directional coupler, a KIDs detector reading circuit module, an adjustable phase shifter, an active mixer circuit module, a filter circuit module, a data acquisition card and a control computer;
the output signal of the frequency synthesis source is divided into two paths by a directional coupler, and the two output ends of the directional coupler are respectively connected with the read signal input end of a KIDs detector read circuit module and the input end of an adjustable phase shifter; the output end of a read signal of the KIDs detector read circuit module is connected with the radio frequency signal input end of the active frequency mixing circuit module, and the output end of the adjustable phase shifter is connected with the local oscillator signal input end of the active frequency mixing circuit module; two paths of intermediate frequency signal output ends of the active mixing circuit module are connected with the data acquisition card through the filter circuit module; the signal output end of the data acquisition card is connected with the signal input end of the control computer, and the signal output end of the control computer is connected with the control signal input end of the frequency synthesis source;
the reading circuit module of the KIDs detector comprises a first adjustable attenuator arranged at the input end of a reading signal, a second adjustable attenuator arranged at the output end of the reading signal, the output end of the first adjustable attenuator is connected with the input end of the first low-temperature attenuator through a first straight spacer, the output end of the first low-temperature attenuator is connected with the input end of the second low-temperature attenuator through a second straight spacer, the output end of the second low-temperature attenuator is connected with the input end of a KIDs detector chip arranged in the sample box, the output end of the KIDs detector chip is connected with the input end of a low-temperature low-noise amplifier, the output end of the low-temperature low-noise amplifier is connected with the input end of a third low-temperature attenuator, the output end of the third low-temperature attenuator is connected with the input end of the normal-temperature low-noise amplifier, and the output end of the normal-temperature low-noise amplifier is connected with the second adjustable attenuator through a third DC isolator; the first and second adjustable attenuators, the first and third DC isolators and the normal-temperature low-noise amplifier are positioned in a normal-temperature environment, the first, second and third low-temperature attenuators, the second DC isolator, the low-temperature low-noise amplifier and the detector chip are arranged in the low-temperature Dewar device, and the second DC isolator is a double-isolation DC isolator;
the active frequency mixing circuit module comprises two Gilbert double-balanced frequency mixers and a multiphase quadrature splitter, and a radio-frequency signal entering the active frequency mixing circuit module is divided into two paths to enter the two Gilbert double-balanced frequency mixers after being converted into a differential signal by a first broadband balun; after local oscillation signals entering the active frequency mixing circuit module are converted into differential signals through a second broadband balun, the differential signals are equally divided into two paths of constant amplitude signals with 90-degree phase difference through the multiphase orthogonal branching unit, then the two paths of constant amplitude signals respectively enter the two Gilbert double-balanced frequency mixers, and differential signals output by the two Gilbert double-balanced frequency mixers are converted into single-port signals through the instrument amplifier respectively and then are output as intermediate frequency signals of the active frequency mixing circuit module;
the filter circuit module is provided with two low-pass filters which are connected with the two instrument amplifiers of the active mixing circuit module in a one-to-one correspondence mode, two paths of intermediate frequency signals of the active mixing circuit module are processed by the low-pass filters and then are sent to the data acquisition card, and the cut-off frequency of the low-pass filters is lower than 1 MHz.
On the basis of the above scheme, a further improved or preferred scheme further comprises:
in the KIDs detector reading circuit module, the adjustable range values of the first adjustable attenuator and the second adjustable attenuator are 0-62 dB, the normal-temperature low-noise amplifier and the low-temperature low-noise amplifier are both +40dB amplifiers, the first low-temperature attenuator is a 10dB attenuator, the second low-temperature attenuator is a 20dB attenuator, and the third low-temperature attenuator is a 3dB attenuator.
The normal-temperature low-noise amplifier is a low-noise amplifier with a noise coefficient not higher than 5dB, and the low-temperature low-noise amplifier is a low-noise amplifier with a noise temperature not higher than 20K.
A KIDs detector noise test method based on the test circuit is characterized by comprising the following steps:
installing a KIDs detector chip to be tested in a sample box of a KIDs detector reading circuit module, adjusting the attenuation quantity of a first adjustable attenuator and a second adjustable attenuator of the input end and the output end of the KIDs detector reading circuit module to be maximum after a test circuit is installed, and starting direct current power supplies of a low-temperature low-noise amplifier, a normal-temperature low-noise amplifier and an instrument amplifier;
setting a frequency synthesis source through a control computer, accurately setting the frequency of the frequency synthesis source to the central frequency of a KIDs detector chip resonator, setting the power level of the frequency synthesis source at 0dBm, and then starting the power output of the frequency synthesis source;
thirdly, the data acquisition card is started through the control computer, so that the data acquisition card keeps a low-speed sampling state with the sampling frequency not higher than 1kHz, the obtained direct current data is displayed on a screen of the control computer in real time and recorded as reference voltage V outputted by I, Q two orthogonal intermediate frequency signalsI0、VQ0The intermediate frequency signal I is a reference signal, and the intermediate frequency signal Q is an orthogonal signal with a phase difference of 90 degrees;
setting the attenuation of the first adjustable attenuator according to the priori knowledge of the detected KIDs detector chip to ensure that the read signal entering the KIDs detector chip is at the optimal level; setting the attenuation of a second adjustable attenuator, and enabling the link gain of a reading circuit module of the KIDs detector to be maximum on the premise of ensuring that the normal-temperature low-noise amplifier is in a linear working area and the mixer is in a fundamental wave mixing area;
adjusting the adjustable phase shifter until the amplitudes of the two orthogonal intermediate frequency signals I, Q are the same, and recording the direct current value V of the output voltage of the two intermediate frequency signals I, Q at the momentI1、VQ1；
Anchoring the feature vector of the noise signal to be measured, and converting VI1、VQ1And V obtained in step (three)I0、VQ0Substituting into formula (1) and formula (2), and calculating the amplitude V of the feature vectorMAnd phase θ:
θ＝tan-1((V11-V10)/(VQ1-VQ0)) (2)
(V) adjusting the data acquisition card to a high-speed acquisition state with the sampling frequency not lower than 1MHz, and continuously acquiring data V for a period of timeIn(t) and VQn(t) the above VIn(t) and VQn(t) time function values of two paths of intermediate frequency signal output voltages are respectively shown, and t is sampling time;
(VI) mixing VI0、VQ0、VM、θ、VIn(t)、VQn(t) substituting the formula (3) and the formula (4), and processing the data obtained in the step (five) by using the formula (3) and the formula (4) to obtain time domain data of the noise signals decomposed into amplitude and phase vector directions;
M(t)＝[(VIn(t)-VI0)cosθ+(VQn(t)-VQ0)sinθ]/VM(3)
Φ(t)＝[-(VIn(t)-VI0)sinθ+(VQn(t)-VQ0)cosθ]/VM(4)。
and (seventhly), performing power spectrum estimation on the time domain data of the noise signal through a computer data processing program to obtain frequency domain data of the KIDs detector chip noise signal.
And (5) the sampling time of the step (five) is not less than 10 s.
Has the advantages that:
1) the invention provides a test circuit which takes a broadband Gilbert double-balanced active quadrature mixer circuit structure as a core module and can complete the noise test work of KIDs detector chips. The Gilbert active quadrature mixer adopts a differential form as an output/input port, so that the common-mode noise interference is effectively reduced. The quadrature mixer has excellent amplitude/phase balance degree and port isolation degree, and parasitic direct current bias generated by an intermediate frequency output port is very weak. Therefore, noise measurement can be accurately carried out, independent calibration of the frequency mixer is not needed, and the measurement process is simplified.
2) Because the gilbert mixer has frequency conversion gain, the amplification factor of a subsequent direct current amplifier is obviously reduced, and the gilbert mixer is also beneficial to improving the dynamic range of a circuit system. In addition, the active frequency mixer adopts the direct current voltage input from the outside to provide the working point bias, and the requirement on the excitation power of the local oscillator is also obviously reduced.
3) The invention uses instrument amplifier as main device to convert the differential intermediate frequency output signal of Gilbert double-balance mixer into single-end intermediate frequency output signal, which can provide proper voltage amplification gain and buffer isolation between the mixer intermediate frequency output end and the A/D converter, and ensure the output voltage always positive (relative to the working voltage), therefore, it can work normally with single polarity voltage.
Drawings
FIG. 1 is a schematic structural diagram of a KIDs detector noise test circuit based on an active quadrature mixer;
FIG. 2 is a schematic diagram of an active mixer circuit module;
FIG. 3 is a schematic diagram of the reading circuit module of the KIDs detector.
Detailed Description
In order to clarify the technical solution of the present invention, the present invention will be further described with reference to the accompanying drawings and specific embodiments.
As shown in figure 1, the KIDs detector noise test circuit based on the active quadrature mixer comprises a frequency synthesis source 1, a directional coupler 2, a KIDs detector reading circuit module 3, an adjustable phase shifter 4, an active mixing circuit module 5, a filter circuit module, a data acquisition card 8, a control computer and the like, and mainly has the function of measuring amplitude and phase noise of a KIDs detector chip.
The signal output end of the frequency synthesis source 1 is connected with a directional coupler 2, the output signal of the frequency synthesis source is divided into two paths by the directional coupler 2, and two output ends of the directional coupler 2 are respectively connected with the signal input end of a KIDs detector reading circuit module 3 and the input end of an adjustable phase shifter 4. The signal output end of the KIDs detector reading circuit module 3 is connected with the radio frequency signal input end of the active frequency mixing circuit module 5, and the output end of the adjustable phase shifter 4 is connected with the local oscillation signal input end of the active frequency mixing circuit module 5; two paths of intermediate frequency signal output ends of the active mixing circuit module 5 are connected with the data acquisition card 8 through the filter circuit module; and the signal output end of the data acquisition card 8 is connected with the signal input end of the control computer, and the signal output end of the control computer is connected with the control signal input end of the frequency synthesis source 1.
In this embodiment, the frequency synthesizer 1 preferably employs a high-stability frequency synthesizer with a finely adjustable frequency, and provides an excitation signal for the KIDs detector chip and a local oscillation signal for the active mixer module 5.
As shown in fig. 3, the KIDs detector readout circuit module 3 includes a first adjustable attenuator 301 disposed at the readout signal input terminal, and a second adjustable attenuator 310 disposed at the readout signal output terminal. The input end of the first adjustable attenuator 301 is connected with one signal output end of the directional coupler 2, the output end of the first adjustable attenuator 301 is connected with the input end of the first low-temperature attenuator 303 through the first straight isolator 302, the output end of the first low-temperature attenuator 303 is connected with the input end of the second low-temperature attenuator 305 through the second straight isolator 304, the output end of the second low-temperature attenuator 305 is connected with the input end of a KIDs detector chip installed in a sample box, the output end of the KIDs detector chip is connected with the input end of a low-temperature low-noise amplifier 306, the output end of the low-temperature low-noise amplifier 306 is connected with the input end of a third low-temperature attenuator 307, the output end of the third low-temperature attenuator 307 is connected with the input end of a normal-temperature low-noise amplifier 308, and the output end of the normal-temperature low-noise amplifier 308 is connected with the, the output end of the second adjustable attenuator 310 is connected to the rf signal input end of the active mixer circuit module 5. The KIDs detector read-out circuit module 3 realizes the thermal isolation among different cold levels through a DC blocking device; the influence of the normal temperature thermal noise outside the Dewar on the core chip of the superconducting KIDs detector is reduced through a low-temperature attenuator; providing signal power amplification through a low-temperature low-noise amplifier and a normal-temperature low-noise amplifier; the input level and the output level are conveniently adjusted to appropriate levels by adjustable attenuators at the radio frequency input and output terminals.
In this embodiment, the first adjustable attenuator, the second adjustable attenuator, the first dc isolator, the third dc isolator, and the normal temperature low noise amplifier 308 are in a normal temperature environment of about 300K, and the first low temperature attenuator, the second low temperature attenuator, the third low temperature attenuator, the second dc isolator 304, the low temperature low noise amplifier 306, and the detector chip are disposed in a low temperature dewar apparatus of about 4.2K. The attenuation of the first low-temperature attenuator 303 is set to 10dB, the attenuation of the second low-temperature attenuator 305 is set to 20dB, and the attenuation of the third low-temperature attenuator 307 is set to 3 dB. The low-temperature low-noise amplifier 306 and the normal-temperature low-noise amplifier 308 both adopt a unit module amplifier or a cascade amplifier with +40dB gain. The second dc isolator 304 adopts double isolation dc isolators, and the attenuation adjustable range of the first and second adjustable attenuators is 0-62 dB. The noise coefficient of the normal temperature low noise amplifier 308 is not higher than 5dB, preferably not higher than 3dB, and the noise temperature of the low temperature low noise amplifier is not higher than 20K (kelvin).
As shown in fig. 2, the active mixer circuit module 5 includes a first gilbert double balanced mixer 503, a second gilbert double balanced mixer 504, a first wideband balun 501, a second wideband balun 502, a multiphase quadrature splitter, a first instrumentation amplifier 505, and a second instrumentation amplifier 506. The rf signal entering the active mixer circuit module 5 is converted into a differential signal by the first broadband balun 501, and then divided into two paths to enter the two gilbert double balanced mixers. The local oscillation signal entering the active frequency mixing circuit module 5 is converted into a differential signal by the second broadband balun 502, and then is divided equally into two paths of equal amplitude signals with a phase difference of 90 ° by the multiphase quadrature splitter, and then enters two gilbert double balanced mixers respectively, and the signal entering the first gilbert double balanced mixer 503 is taken as a reference signal, and enters the quadrature signal of the second gilbert double balanced mixer 504. The first gilbert double balanced mixer 503 is connected to the first instrumentation amplifier 505, converts the output differential signal into a single-port signal through the first instrumentation amplifier 505, and outputs the single-port signal as one intermediate frequency signal of the active mixer circuit module 5, which is set as I; the second gilbert double balanced mixer 504 is connected to the second instrumentation amplifier 506, and converts the output differential signal into a single-port signal through the second instrumentation amplifier 506, and outputs the single-port signal as another intermediate frequency signal of the active mixer circuit module 5, which is Q. The two paths of intermediate frequency signals complete the conversion from differential signals to single-ended signals through an amplifying circuit of the instrument amplifier, and can provide certain voltage gain to facilitate the acquisition of a subsequent high-speed data acquisition card. In the active mixing circuit module 5, each internal port of the mixer adopts a differential form as an output/input port, and the differential form effectively ensures the symmetry of the circuit and reduces the common-mode noise interference. Most microwave signal sources still adopt a single-port form, so that a broadband balun is adopted as a device for realizing single-end-differential conversion between an internal circuit and an external circuit of a local oscillator/radio frequency port. The number of required analog-to-digital converters can also be halved after the intermediate frequency output signal has been converted to single-ended form.
The local oscillator port of the active frequency mixing circuit module 5 is connected in series with a broadband coaxial adjustable phase shifter 4, and the function of the phase shifter is to change the relative phase difference between the local oscillator signal and the radio frequency signal, so that the amplitude of two paths of orthogonal intermediate frequency output signals of the active frequency mixing circuit module 5 is adjusted, and the influence of parasitic direct current bias voltage on a test result is reduced. In the data acquisition process of the embodiment, the parasitic direct-current bias voltage of the two intermediate-frequency outputs is less than 10mV, and because the gilbert double-balanced mixer and the multiphase quadrature splitter are mostly manufactured into a microwave integrated circuit chip by adopting a mature microelectronic process at present, the structural symmetry and the high-precision processing of the mature microelectronic process guarantee that the amplitude error of the two intermediate-frequency outputs is less than 0.1dBc and the quadrature phase error is less than 1 degree, the gilbert double-balanced mixer can be considered to be close to an ideal quadrature mixer in the scheme of the application, and a special calibration process for the mixer is not needed. Meanwhile, in the embodiment, the local oscillation excitation level required by the gilbert double-balanced mixer is controlled to be about 0dBm, and compared with the level required by the passive quadrature mixer in the traditional homodyne mixing phase noise measurement scheme which is at least larger than 13dBm, the frequency synthesis power level of the frequency synthesis source can be reduced by one magnitude.
The filter circuit module is provided with a first low-pass filter 6 and a second low-pass filter 7 which are respectively connected with a first instrument amplifier and a second instrument amplifier, two paths of intermediate frequency signals of the active mixing circuit module 5 are processed by the low-pass filters and then sent to the data acquisition card 8, signals output by the intermediate frequency of the mixing circuit module 5 are quasi-direct-current phase noise signals, the cut-off frequency of the required low-pass filters is lower than 1MHz, a differential passive low-pass filter can be designed by an LC surface-mounted element, and an appropriate active filter integrated circuit chip can be selected.
The data acquisition card 8 selects a high-precision data acquisition card with data acquisition frequency of more than 1MHz and precision of more than 16 bits to realize signal acquisition with high signal-to-noise ratio and improve phase noise measurement precision.
The test circuit of the invention also comprises a control computer (not shown), and the function of the control computer is mainly to realize the control of the frequency synthesizer 1 (frequency synthesizer) and the data acquisition card 8, and the data processing of the noise performance measurement of the KIDs detector chip, etc.
A KIDs detector noise test method based on the test circuit comprises the following steps:
firstly, a KIDs detector chip to be tested is installed in a sample box of a KIDs detector reading circuit module 3, after a test circuit is installed, the attenuation quantities of a first adjustable attenuator and a second adjustable attenuator at the input end and the output end of the KIDs detector reading circuit module 3 are adjusted to be maximum, so that the initial excitation level of a low noise amplifier is prevented from being saturated or damaged due to overlarge level; then starting the direct current power supplies of the low-temperature low-noise amplifier, the normal-temperature low-noise amplifier and the instrument amplifier;
secondly, setting a frequency synthesis source through a control computer, accurately setting the frequency of the frequency synthesis source to the central frequency of a KIDs detector chip resonator, setting the power level of the frequency synthesis source at 0dBm, and then starting the frequency synthesis source 1 to output power;
thirdly, the data acquisition card is started through the control computer, so that the data acquisition card keeps a low-speed sampling state with the sampling frequency not higher than 1kHz, the obtained direct current data is displayed on a screen of the control computer in real time and recorded as reference voltage V outputted by I, Q two orthogonal intermediate frequency signalsI0、VQ0The intermediate frequency signal I is a reference signal, and the intermediate frequency signal Q is an orthogonal signal with a phase difference of 90 degrees;
setting the attenuation of the first adjustable attenuator according to the priori knowledge of the detected KIDs detector chip to ensure that the read signal entering the KIDs detector chip is at the optimal level; setting the attenuation of a second adjustable attenuator, and enabling the link gain of a reading circuit module of the KIDs detector to be maximum on the premise of ensuring that the normal-temperature low-noise amplifier is in a linear working area and the mixer is in a fundamental wave mixing area;
adjusting the adjustable phase shifter until the amplitudes of the two orthogonal intermediate frequency signals I, Q are basically the same, and recording the direct current value V of the output voltage of the two intermediate frequency signals I, Q at the momentI1、VQ1；
Anchoring the feature vector of the noise signal to be measured, and converting VI1、VQ1And V obtained in step (three)I0、VQ0Substituting into formula (1) and formula (2), and calculating the amplitude V of the feature vectorMAnd phase θ:
θ＝tan-1((VI1-VI0)/(VQ1-VQ0)) (2)
(V) adjusting the data acquisition card to a high-speed acquisition state with the sampling frequency not lower than 1MHz, and continuously acquiring data V of more than 10sIn(t) and VQn(t) the above VIn(t) and VQn(t) time function values of two paths of intermediate frequency signal output voltages are respectively shown, and t is sampling time;
(VI) mixing VI0、VQ0、VM、θ、VIn(t)、VQn(t) substituting the formula (3) and the formula (4), and processing the data obtained in the step (five) by using the formula (3) and the formula (4) to obtain time domain data of the noise signals decomposed into amplitude and phase vector directions;
M(t)＝[(VIn(t)-VI0)cosθ+(VQn(t)-VQ0)sinθ]/VM(3)
Φ(t)＝[-(VIn(t)-VI0)sinθ+(VQn(t)-VQ0)cosθ]/VM(4)
and (seventhly), performing power spectrum estimation on the time domain data of the noise signal through a computer data processing program to obtain frequency domain data of the KIDs detector chip noise signal.
In the step (IV), the two paths of orthogonal intermediate frequency outputs are adjusted to have the same size, which is beneficial to effectively utilizing the bit of the data acquisition card and reducing the influence of parasitic direct current bias on the test result to the minimum.
The foregoing shows and describes the general principles, essential features, and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the foregoing description only for the purpose of illustrating the principles of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the invention as defined by the appended claims, specification, and equivalents thereof.
Claims (6)
1. A KIDs detector noise test circuit based on an active quadrature mixer is characterized by comprising a frequency synthesis source (1), a directional coupler (2), a KIDs detector reading circuit module (3), an adjustable phase shifter (4), an active mixing circuit module (5), a filter circuit module, a data acquisition card (8) and a control computer;
the output signal of the frequency synthesis source (1) is divided into two paths through a directional coupler (2), and the two output ends of the directional coupler (2) are respectively connected with the read signal input end of a KIDs detector read circuit module (3) and the input end of an adjustable phase shifter (4); the read signal output end of the KIDs detector read circuit module (3) is connected with the radio frequency signal input end of the active frequency mixing circuit module (5), and the output end of the adjustable phase shifter (4) is connected with the local oscillation signal input end of the active frequency mixing circuit module (5); two paths of intermediate frequency signal output ends of the active mixing circuit module (5) are connected with a data acquisition card (8) through a filter circuit module; the signal output end of the data acquisition card (8) is connected with the signal input end of the control computer, and the signal output end of the control computer is connected with the control signal input end of the frequency synthesizer source (1);
the KIDs detector reading circuit module (3) comprises a first adjustable attenuator (301) arranged at a reading signal input end and a second adjustable attenuator (310) arranged at a reading signal output end, wherein the output end of the first adjustable attenuator (301) is connected with the input end of a first low-temperature attenuator (303) through a first straight-blocking device (302), the output end of the first low-temperature attenuator (303) is connected with the input end of a second low-temperature attenuator (305) through a second straight-blocking device (304), the output end of the second low-temperature attenuator (305) is connected with the input end of a KIDs detector chip arranged in a sample box, the output end of the KIDs detector chip is connected with the input end of a low-temperature low-noise amplifier (306), the output end of the low-temperature low-noise amplifier (306) is connected with the input end of a third low-temperature attenuator (307), and the output end of the third low-temperature attenuator (307) is connected with the input end of a normal-temperature low-noise, the output end of the normal-temperature low-noise amplifier (308) is connected with a second adjustable attenuator (310) through a third DC isolator (309); the first and second adjustable attenuators, the first and third DC isolators and the normal-temperature low-noise amplifier (308) are positioned in a normal-temperature environment, the first, second and third low-temperature attenuators, the second DC isolator (304), the low-temperature low-noise amplifier (306) and the detector chip are arranged in the low-temperature Dewar device, and the second DC isolator (304) is a double-isolation DC isolator;
the active frequency mixing circuit module (5) comprises two Gilbert double-balanced mixers (503, 504) and a multiphase quadrature splitter, and a radio-frequency signal entering the active frequency mixing circuit module (5) is divided into two paths to enter the two Gilbert double-balanced mixers after being converted into a differential signal through a first broadband balun (501); after local oscillation signals entering the active frequency mixing circuit module (5) are converted into differential signals through a second broadband balun (502), the differential signals are divided into two paths of constant amplitude signals with 90-degree phase difference through the multiphase orthogonal branching unit, then the two paths of constant amplitude signals enter the two Gilbert double-balanced frequency mixers respectively, and differential signals output by the two Gilbert double-balanced frequency mixers (503, 504) are converted into single-port signals through the instrumentation amplifiers respectively and then are output as intermediate frequency signals of the active frequency mixing circuit module (5);
the filter circuit module is provided with two low-pass filters which are connected with the two instrument amplifiers of the active mixing circuit module (5) in a one-to-one correspondence mode, two paths of intermediate frequency signals of the active mixing circuit module (5) are processed by the low-pass filters and then are sent to the data acquisition card (8), and the cut-off frequency of the low-pass filters is lower than 1 MHz.
2. The active quadrature mixer-based KIDs detector noise test circuit of claim 1, wherein:
in the KIDs detector reading circuit module (3), the adjustable range values of the first adjustable attenuator and the second adjustable attenuator are 0-62 dB, the normal-temperature low-noise amplifier and the low-temperature low-noise amplifier are +40dB amplifiers, the first low-temperature attenuator (303) is a 10dB attenuator, the second low-temperature attenuator (305) is a 20dB attenuator, and the third low-temperature attenuator (307) is a 3dB attenuator.
3. The active quadrature mixer-based KIDs detector noise test circuit of claim 1, wherein:
the normal-temperature low-noise amplifier (308) is a low-noise amplifier with a noise coefficient not higher than 5dB, and the low-temperature low-noise amplifier (306) is a low-noise amplifier with a noise temperature not higher than 20K.
4. A KIDs detector noise testing method based on a test circuit according to any of claims 1-3, characterized in that it comprises the steps of:
installing a KIDs detector chip to be tested in a sample box of a KIDs detector reading circuit module, adjusting the attenuation quantity of a first adjustable attenuator and a second adjustable attenuator at the input end and the output end of the KIDs detector reading circuit module to be maximum after a test circuit is installed, and starting direct current power supplies of a low-temperature low-noise amplifier, a normal-temperature low-noise amplifier and an instrument amplifier;
setting a frequency synthesis source through a control computer, accurately setting the frequency of the frequency synthesis source to the central frequency of a KIDs detector chip resonator, setting the power level of the frequency synthesis source at 0dBm, and then starting the power output of the frequency synthesis source;
thirdly, the data acquisition card is started through the control computer, so that the data acquisition card keeps a low-speed sampling state with the sampling frequency not higher than 1kHz, the obtained direct current data is displayed on a screen of the control computer in real time and recorded as reference voltage V outputted by I, Q two orthogonal intermediate frequency signalsI0、VQ0The intermediate frequency signal I is a reference signal, and the intermediate frequency signal Q is an orthogonal signal with a phase difference of 90 degrees;
setting the attenuation of the first adjustable attenuator according to the priori knowledge of the detected KIDs detector chip to ensure that the read signal entering the KIDs detector chip is at the optimal level; setting the attenuation of a second adjustable attenuator, and enabling the link gain of a reading circuit module of the KIDs detector to be maximum on the premise of ensuring that the normal-temperature low-noise amplifier is in a linear working area and the mixer is in a fundamental wave mixing area;
adjusting the adjustable phase shifter until the amplitudes of the two orthogonal intermediate frequency signals I, Q are the same, and recording the output power of the two intermediate frequency signals I, Q at the momentDC value V of voltageI1、VQ1；
Anchoring the feature vector of the noise signal to be measured, and converting VI1、VQ1And V obtained in step (three)I0、VQ0Substituting into formula (1) and formula (2), and calculating the amplitude V of the feature vectorMAnd phase θ:
θ＝tan-1((V11-V10)/(VQ1-VQ0)) (2)
(V) adjusting the data acquisition card to a high-speed acquisition state with the sampling frequency not lower than 1MHz, and continuously acquiring data V for a period of timeIn(t) and VQn(t) the above VIn(t) and VQn(t) time function values of two paths of intermediate frequency signal output voltages are respectively shown, and t is sampling time;
(VI) mixing VI0、VQ0、VM、θ、VIn(t)、VQn(t) substituting the formula (3) and the formula (4), and processing the data obtained in the step (five) by using the formula (3) and the formula (4) to obtain time domain data of the noise signals decomposed into amplitude and phase vector directions;
M(t)＝[(VIn(t)-VI0)cosθ+(VQn(t)-VQ0)sinθ]/VM(3)
Φ(t)＝[-(VIn(t)-VI0)sinθ+(VQn(t)-VQ0)cosθ]/VM(4)。
5. the KIDs detector noise testing method of claim 4, further comprising the steps of:
and (seventhly), performing power spectrum estimation on the time domain data of the noise signal through a computer data processing program to obtain frequency domain data of the KIDs detector chip noise signal.
6. The KIDs detector noise testing method of claim 4, wherein the sampling time of step (five) is not less than 10 s.
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