CN105842552B - A kind of microwave receiver noise-measuring system and measurement method - Google Patents
A kind of microwave receiver noise-measuring system and measurement method Download PDFInfo
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Abstract
The present invention relates to a kind of noise-measuring systems of microwave receiver, including：Reference source, feed, data acquisition unit, host computer real-time display unit；Wherein, then microwave signal is input in microwave receiver to be measured by the feed for receiving the microwave signal from air and reference source；Microwave receiver to be measured carries out microwave signal down coversion, amplification, filtering, detection, integral and low frequency enhanced processing, and output voltage signal successively；The voltage signal of the data acquisition unit acquisition and storage receiver output, and it is sent to the host computer real-time display unit；The host computer real-time display unit is handled voltage signal according to the reference source of observation, obtains receiver noise temperature and noise coefficient, and do real-time display to voltage signal, receiver noise temperature and noise coefficient.
Description
Technical Field
The invention relates to the field of noise measurement, in particular to a microwave receiver noise measurement device and a measurement method.
Background
In the working process of the receiver, the signal-to-noise ratio and the sensitivity of signals are limited due to the addition of the noise of the receiver, and particularly, the signals received by the microwave receiver are weak, so the noise characteristic is particularly important, and the noise has direct influence on the sensitivity of a system.
The noise temperature and the noise coefficient of the receiver are used as key indexes for measuring the receiver, and a measurement mode at present adopts a known noise source and noise coefficient analyzer to carry out measurement. Driving a receiver to be tested by using noise generated by a noise source, and measuring the output of the receiver to be tested by using a noise coefficient analyzer; since the noise coefficient analyzer knows the input noise and the signal-to-noise ratio of the noise source, the noise coefficient of the receiver under test can be internally calculated and directly displayed on the screen. Although noise figure analyzers are the most direct method of measuring noise figures, this method has the disadvantages of: 1) the frequency of a receiver measured by a noise coefficient analyzer is limited by the frequency of a known noise source, a universal noise source adopts a diode with low junction capacitance, the frequency is generally lower than 50GHz, and a high-frequency noise source needs to be imported from abroad and is expensive, so that the method cannot meet the requirement of measuring the noise coefficient of the high-frequency receiver; 2) the error of noise measurement by the noise figure analyzer increases rapidly with increasing noise figure of the receiver, so the method is only suitable for receivers with lower noise figures.
Another method of noise figure measurement is calculated by measuring the receiver gain and output power spectral density. The available noise power of the device is:
PNA KT Δ F, where K is boltzmann constant (1.38 × 10)23joules/K), T is temperature (in kelvin K), af is noise bandwidth (in hertz Hz);
when the room temperature is 290K, the noise power spectral density is: PNAD-174 dBm/Hz;
the noise figure is therefore given by the following equation:
NF＝PNOUT-(-174dBm/Hz+20log10(BW)+Gain)
wherein, PNOUT is the measured total output noise power, BW is the frequency bandwidth of the receiver, Gain is the Gain of the receiver, and NF is the noise coefficient of the receiver, and when-174 dBm/Hz is 290K, the power spectral density of the environmental noise is the measured total output noise power.
To simplify the equation, the output noise power spectral density (dBm/Hz) can be measured directly, which becomes:
NF＝PNOUTD+174dBm/Hz-Gain
this method requires a predetermined receiver gain and output power spectral density, which can be measured by a spectrum analyzer, and has the disadvantages that: the measured noise power spectral density is limited by the noise floor of the spectrum analyzer, and when the noise figure is low (generally less than 10dB), (PNOUTD-Gain) is close to-170 dBm/Hz, and when the receiver Gain is 20dB, the noise power spectral density of-150 dBm/Hz needs to be measured, which is lower than the noise floor of most spectrum analyzers. This method is therefore suitable for cases where the system gain is high or the noise figure is very high (e.g. above 30 dB).
Disclosure of Invention
The invention aims to overcome the defect that the noise measuring device and method for the microwave receiver in the prior art have a narrow application range, thereby providing the measuring device and method which have the advantages of wide application range and simple and visual test process.
In order to achieve the above object, the present invention provides a noise measuring apparatus of a microwave receiver, comprising: the device comprises a calibration source, a feed source, a data acquisition unit and an upper computer real-time display unit; wherein,
the feed source is used for receiving microwave radiation signals from the atmosphere and the calibration source and then inputting the microwave radiation signals into a microwave receiver to be tested; the microwave receiver to be tested sequentially performs down-conversion, amplification, filtering, demodulation, integration and low-frequency amplification on the microwave radiation signal and outputs a voltage signal; the data acquisition unit acquires and stores voltage signals output by the receiver and transmits the voltage signals to the upper computer real-time display unit; and the upper computer real-time display unit processes the voltage signal according to the observed calibration source to obtain the noise temperature and the noise coefficient of the receiver and displays the voltage signal, the noise temperature and the noise coefficient of the receiver in real time.
In the above technical solution, the calibration source includes a cold source and a heat source; the cold source is a microwave absorption blackbody cooled by liquid nitrogen and used as a low-temperature reference source; the heat source is a normal-temperature calibration blackbody, provides standard bright temperature equivalent to the ambient temperature, and serves as a high-temperature reference source.
In the technical scheme, the acquisition rate of the data acquisition unit is 0-200 KHz, and the acquisition rate can be adjusted.
The invention also provides a measuring method realized by the noise measuring device of the microwave receiver, which comprises the following steps:
step 1), electrifying a microwave receiver to be tested, and confirming that the system works normally;
step 2), displaying the output voltage of the microwave receiver through a real-time display unit of the upper computer, aligning a feed source to a cold source after the output of the microwave receiver is stable, recording the output voltage of the microwave receiver when the cold source is observed, and calculating the average value;
step 3), aligning the feed source to a heat source, recording the output voltage of the microwave receiver and calculating an average value;
step 4), the following relation exists between the output voltage of the microwave receiver and the noise temperature of the receiver:
VL＝G(Trec+TL)
VH＝G(Trec+TH) (1)
wherein, VLThe average value of output voltage when a cold source is observed for a receiver; t isLThe temperature of the liquid nitrogen cold source is 80K; vHThe average value of the output voltage when the receiver observes the heat source; t isHCalibrating the temperature of the black body at normal temperature, and measuring the environmental temperature in the environment; g is the receiver gain; t isrecIs the receiver noise temperature; wherein the receiver noise temperature TrecAnd the receiver gain G is an unknown quantity;
calculating the noise temperature T of the receiver according to the equation (1)recAnd the receiver gain G is displayed in real time by the real-time display unit of the upper computer;
step 5), the following relation exists between the noise temperature and the noise coefficient of the microwave receiver:
Trec＝(F-1)T0NF＝10·log10F (2)
wherein NF is the noise coefficient of the receiver; f is the noise factor of the receiver; t is0Is ambient temperature;
and (3) calculating to obtain a noise coefficient F of the receiver according to the equation (2), and displaying in real time by a real-time display unit of the upper computer.
The invention has the advantages that:
1. the noise measuring device does not need the cooperation of a noise coefficient analyzer or a frequency spectrograph, and noise measuring errors are not accumulated and cannot be increased along with the increase of the noise coefficient of the receiver;
2. the noise measuring device has the advantages of simple test process, visual result display and convenient carrying, and is particularly suitable for field tests and the like.
Drawings
Fig. 1 is a schematic configuration diagram of a noise measuring apparatus of a microwave receiver of the present invention;
FIG. 2 is a schematic diagram of a microwave receiver under test;
fig. 3 is a flowchart of a noise measurement method of a microwave receiver of the present invention.
Detailed Description
The invention will now be further described with reference to the accompanying drawings.
Fig. 1 is a schematic structural diagram of a noise measurement device of a microwave receiver according to the present invention. As shown in the figure, the noise measuring device comprises a calibration source, a feed source, a data acquisition unit and an upper computer real-time display unit; the feed source is used for receiving microwave radiation signals from the atmosphere and a calibration source and then inputting the microwave radiation signals into a microwave receiver to be tested; the microwave receiver to be tested sequentially performs down-conversion, amplification, filtering, demodulation, integration and low-frequency amplification on the microwave radiation signal and outputs a voltage signal; the data acquisition unit acquires and stores voltage signals output by the receiver and transmits the voltage signals to the upper computer real-time display unit; and the upper computer real-time display unit processes the voltage signal according to the observed calibration source to obtain the noise temperature and the noise coefficient of the receiver and displays the voltage signal, the noise temperature and the noise coefficient of the receiver in real time.
The components of the noise measuring device of the present invention will be further described below.
The calibration source comprises a cold source and a heat source; the cold source is a microwave absorption blackbody cooled by liquid nitrogen and used as a low-temperature reference source; the heat source is a normal-temperature calibration blackbody, provides standard bright temperature equivalent to the ambient temperature, and serves as a high-temperature reference source.
The data acquisition unit has the acquisition rate of 0-200 KHz and is adjustable.
Fig. 2 is a schematic structural diagram of a microwave receiver to be tested, and as shown in the figure, the microwave receiver to be tested includes: the system comprises a local oscillator, a low-noise amplifier, a mixer, an intermediate frequency amplifier, a filter, a detector, an integrator and a low-frequency amplifier; the signal received by the feed source is amplified by radio frequency, then frequency down-conversion from radio frequency to intermediate frequency is completed by the local oscillator and the mixer, then the signal is amplified by the intermediate frequency amplifier, finally the conversion from intermediate frequency to low frequency is completed by the detector, the low frequency signal is smoothed by the integrator, and finally the signal is amplified by the low frequency and output to the data acquisition unit for data processing. In addition, based on the structure of the receiver, the working frequency of the receiver unit is not limited, and after down-conversion, amplification, filtering, detection, integration and low-frequency amplification processing, the output voltage signal range is-10V.
The noise measurement device of the invention can realize the noise measurement of the microwave receiver, and as shown in figure 3, the noise measurement method of the invention comprises the following steps:
1) electrifying the microwave receiver to confirm that the system works normally;
2) the output voltage of the microwave receiver is displayed through the upper computer real-time display unit, when the output of the microwave receiver is stable, the feed source is aligned to the cold source, the output voltage of the microwave receiver when the cold source is observed is recorded, and the average value is calculated;
3) aligning the feed source to a heat source, simultaneously recording the output voltage of the microwave receiver, and calculating an average value;
4) since a microwave receiver can be considered as a linear system, the following relationship exists between the receiver output voltage and the receiver noise temperature:
VL＝G(Trec+TL)
VH＝G(Trec+TH) (1)
wherein, VLThe average value of output voltage when a cold source is observed for a receiver; t isLThe temperature of the liquid nitrogen cold source is 80K; vHThe average value of the output voltage when the receiver observes the heat source; t isHCalibrating the temperature of the black body at normal temperature, and measuring the environmental temperature in the environment; g is the receiver gain; t isrecIs the receiver noise temperature; wherein the receiver noise temperature TrecAnd the receiver gain G is an unknown quantity.
From said equation (1), the receiver noise temperature T can be derivedrecAnd the receiver gain G is displayed in real time by the real-time display unit of the upper computer;
5) the following relationship exists between the noise temperature and the noise figure of the receiver:
Trec＝(F-1)T0NF＝10·log10F (2)
wherein NF is the noise coefficient of the receiver; f is the noise factor of the receiver; t is0Is ambient temperature;
and (3) obtaining the noise coefficient F of the receiver through the equation (2), and displaying the noise coefficient F in real time by the real-time display unit of the upper computer.
In conclusion, the noise measurement device and the measurement method of the microwave receiver can realize the measurement of the noise temperature and the noise coefficient of the receiver without the cooperation of a spectrum analyzer, a noise coefficient analyzer and a noise source in the test process, save the cost, have simple test process and are convenient to operate; in addition, no limiting condition is provided for the working frequency and the noise coefficient of the receiver, the application is wide, and the practicability is high.
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and are not limited. Although the present invention has been described in detail with reference to the embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (3)
1. A measurement method realized by a noise measurement device based on a microwave receiver is characterized by comprising the following steps:
step 1), electrifying a microwave receiver to be tested, and confirming that the system works normally;
step 2), displaying the output voltage of the microwave receiver through a real-time display unit of the upper computer, aligning a feed source to a cold source after the output of the microwave receiver is stable, recording the output voltage of the microwave receiver when the cold source is observed, and calculating the average value;
step 3), aligning the feed source to a heat source, recording the output voltage of the microwave receiver and calculating an average value;
step 4), the following relation exists between the output voltage of the microwave receiver and the noise temperature of the receiver:
VL＝G(Trec+TL)
VH＝G(Trec+TH) (1)
wherein, VLThe average value of output voltage when a cold source is observed for a receiver; t isLThe temperature of the liquid nitrogen cold source is 80K; vHThe average value of the output voltage when the receiver observes the heat source; t isHCalibrating the temperature of the black body at normal temperature, and measuring the environmental temperature in the environment; g is the receiver gain; t isrecIs the receiver noise temperature; wherein the receiver noise temperature TrecAnd the receiver gain G is an unknown quantity;
calculating the noise temperature T of the receiver according to the equation (1)recAnd the receiver gain G is displayed in real time by the real-time display unit of the upper computer;
step 5), the following relation exists between the noise temperature and the noise coefficient of the microwave receiver:
Trec＝(F-1)T0NF＝10·log10F (2)
wherein NF is the noise coefficient of the receiver; f is the noise factor of the receiver; t is0Is ambient temperature;
calculating to obtain a noise coefficient F of the receiver according to the equation (2), and displaying in real time by an upper computer real-time display unit;
wherein, the noise measuring device of the microwave receiver comprises: the device comprises a calibration source, a feed source, a data acquisition unit and an upper computer real-time display unit; wherein,
the feed source is used for receiving microwave radiation signals from the atmosphere and the calibration source and then inputting the microwave radiation signals into a microwave receiver to be tested; the microwave receiver to be tested sequentially performs down-conversion, amplification, filtering, demodulation, integration and low-frequency amplification on the microwave radiation signal and outputs a voltage signal; the data acquisition unit acquires and stores voltage signals output by the receiver and transmits the voltage signals to the upper computer real-time display unit; and the upper computer real-time display unit processes the voltage signal according to the observed calibration source to obtain the noise temperature and the noise coefficient of the receiver and displays the voltage signal, the noise temperature and the noise coefficient of the receiver in real time.
2. The measurement method of claim 1, wherein the calibration source comprises a cold source and a heat source; the cold source is a microwave absorption blackbody cooled by liquid nitrogen and used as a low-temperature reference source; the heat source is a normal-temperature calibration blackbody, provides standard bright temperature equivalent to the ambient temperature, and serves as a high-temperature reference source.
3. The measurement method according to claim 1, wherein the data acquisition unit has an acquisition rate of 0 to 200KHz, and the acquisition rate can be adjusted.
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| CN108650036B (en) * | 2018-05-03 | 2020-08-04 | 中国科学院新疆天文台 | Calibration method for single-beam refrigeration receiver |
| CN109302246B (en) * | 2018-09-25 | 2020-12-25 | 中国科学院新疆天文台 | K-band receiver noise temperature testing method |
| CN110231516B (en) * | 2019-06-14 | 2021-05-11 | 北京无线电计量测试研究所 | Quick variable temperature microwave noise source |
| CN111835439B (en) * | 2020-07-27 | 2021-11-19 | 中国电子科技集团公司第五十四研究所 | Method for measuring noise coefficient of tuner of integrated satellite television |
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