Mixer single-sideband noise coefficient measurement system and method for removing image frequency influence

Abstract

The invention provides a frequency mixer single-sideband noise coefficient measurement system and method capable of removing image frequency influence, and relates to the technical field of microwave and radio frequency. According to the method, a frequency mixer single-sideband noise coefficient measurement system is adopted; a frequency mixer double-sideband noise coefficient and single-sideband noise coefficient conversion model is constructed through a difference value between an input noise power theoretical calculation value calculated based on measured noise source excess noise ratio data and an input noise actual power value actually input into a measured frequency mixer to participate in frequency mixing; the single-sideband noise coefficient of the frequency mixer to be measured is accurately calculated by using the frequency mixer double-sideband noise coefficient and single-sideband noise coefficient conversion model, so that an input filter only needs to filter higher harmonic frequency mixing noise signals during measurement without filtering image frequency noise signals, the requirement on performance indexes of the input filter is reduced, and the measurement accuracy is improved. The measurement difficulty is reduced, and meanwhile, the problem that the single-sideband noise coefficient of the mixer is difficult to accurately evaluate due to the fact that the image frequency noise signal cannot be filtered out is effectively solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of microwave and radio frequency technology, and particularly relates to a mixer single sideband noise figure measurement system and method for removing mirror frequency influence. BACKGROUND

[0002] Any circuit system will generate noise, which limits the ability of the circuit system to receive and process weak signals. As one of the important parameters for quantifying the ability of the circuit to process weak signals, the noise figure is closely related to the technology progress of electronic devices and equipment such as microwave millimeter wave communication, radar, navigation, precision guidance, and improved receiver technology. An important aspect is to reduce the noise generated by the receiver itself as much as possible. With the rapid development of equipment technology, the demand for low-noise devices is becoming more and more urgent, and higher requirements are put forward for the measurement precision of the noise figure index. High-precision noise figure measurement is of great significance for optimizing the size, weight, cost and performance of the whole machine and improving the reliability of the system.

[0003] At present, the noise figure analyzer is commonly used to measure the noise figure of the measured object. The measurement principle is based on the Y-factor method. The ratio of the output noise power of the measured object under the hot-state and cold-state excitation of the noise source is measured to determine the Y-factor. After operation and processing, the noise figure of the measured object is obtained. As a common measured object, the mixer is often used to move the frequency of the processed signal to a specified frequency band and is a key device in the transmit front end and the receive front end. The noise figure of the mixer itself has a great influence on the noise performance index of the entire transmit front end and the receive front end. In order to accurately evaluate the noise figure performance index of the entire transmit front end and the receive front end, it is usually necessary to accurately measure the single sideband noise figure of the mixer, i.e. the noise figure measurement result of the mixer under the excitation of a specified sideband frequency noise signal.

[0004] When the noise figure is measured by using the noise figure analyzer, the noise source is used as a calibration source and a measurement excitation source. The output noise signal of the noise source is a wide spectrum signal, which is distributed in a very wide frequency band. During the measurement of the noise figure of the mixer, the noise signals at the mixer radio frequency, mirror frequency and various high-order harmonic mixing frequencies output by the noise source will participate in the mixing. However, when the accurate single sideband noise figure of the mixer is measured, it is required that only the noise signal at the mixer radio frequency participates in the mixing. If there is no special filter circuit inside the mixer, a filter needs to be connected to the input of the mixer to filter out various unnecessary noise signals. The error introduced by the loss of the filter can be corrected by the loss compensation function.

[0005] At present, when measuring the single sideband noise figure of a mixer, the mirror frequency noise signal and various high harmonic mixing noise signals output by a noise source need to be filtered out through an input filter. If the intermediate frequency output signal frequency is low, the interval between the radio frequency of the mixer and the mirror frequency is small. Since the actual filter is not an ideal filter, there are limitations of bandwidth and transition band, and the precise measurement of the single sideband noise figure of the mixer cannot be realized by filtering out the unwanted mirror frequency noise signal. The commonly used alternative method at present is to directly give the double sideband noise figure measurement result without filtering out the mirror frequency signal, and the designer estimates the corresponding single sideband noise figure performance index according to experience, or simply considers that the double sideband noise figure is 3dB lower than the single sideband noise figure. It is difficult to accurately measure the single sideband noise figure performance index of the mixer, which leads to the fact that the design result cannot meet the design requirements. Moreover, it is difficult to give the precise numerical relationship between the single sideband noise figure and the double sideband noise figure of the mixer at present, and only the experience of the designer can be relied on to set the parameters, which cannot meet the design requirements of all application scenarios. SUMMARY

[0006] In order to solve the problem that the prior art cannot accurately measure the single sideband noise figure of a mixer, the present application provides a mixer single sideband noise figure measurement system and method for removing the influence of mirror frequency, which only needs to filter out the high harmonic mixing noise signal through the input filter during measurement, and no longer requires filtering out the mirror frequency noise signal, thereby reducing the performance index requirements of the input filter, reducing the measurement difficulty, effectively solving the influence of the mirror frequency noise signal on the accurate measurement of the single sideband noise figure of the mixer, and providing technical support for guiding the design of the mixer.

[0007] In order to achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0008] A mixer single sideband noise figure measurement system for removing the influence of mirror frequency, comprising a noise source, an input filter, a measured mixer, an output filter, a local oscillator source and a noise figure analyzer;

[0009] The noise source, the input filter, the measured mixer and the output filter are connected in sequence, the noise source is connected with the input filter during measurement and connected with the noise figure analyzer during calibration;

[0010] The noise figure analyzer is connected with the local oscillator source through a local oscillator control bus and a common time base interface, controls the frequency and power of the local oscillator source through the local oscillator control interface, and ensures that the reference frequency of the noise figure analyzer and the local oscillator source is the same through the common time base connection.

[0011] Preferably, the noise source is a calibration noise source or a measurement noise source, the calibration noise source is used for calibrating the noise figure analyzer, and the measurement noise source is used for measuring the single sideband noise figure of the mixer.

[0012] A method for measuring the single sideband noise figure of a mixer by removing the mirror frequency effect, using the system for measuring the single sideband noise figure of a mixer by removing the mirror frequency effect as described above, comprising the following steps:

[0013] Step 1, select a calibration noise source for noise figure analyzer calibration;

[0014] Load the super noise ratio of the calibration noise source for noise figure analyzer calibration, and determine the linear value of the super noise ratio of the calibration noise source at each measurement frequency point as ENR IFCAL,i ;

[0015] Step 2, set the measurement mode;

[0016] Select the upconverter measurement mode or the downconverter measurement mode, set the single sideband measurement mode, set the mode and power of the local oscillator, set the radio frequency, local oscillator and intermediate frequency of the measured mixer, set the number of measurement frequency points and the number of averages;

[0017] Step 3, edit the loss characteristics of the input filter and the output filter in the noise figure analyzer;

[0018] Step 4, set the mirror frequency rejection ratio of the measured mixer at each measurement frequency point;

[0019] Step 5, connect the calibration noise source and the noise figure analyzer for calibration, control the calibration noise source to work in the source open hot state and the source off cold state respectively, obtain the linear measurement value of the hot power N IFCALH,i and the linear measurement value of the cold power N IFCALC,i of the noise figure analyzer at each measurement frequency point, determine the linear value of the Y factor Y 2IFCAL,i , the linear value of the local noise figure F 2IFCAL,i and the linear value of the gain bandwidth product kGB 2IFCAL,i of the noise figure analyzer at each measurement frequency point;

[0020] Step 6, if the calibration noise source is the same as the measurement noise source, use the calibration noise source as the measurement noise source, if the calibration noise source is different from the measurement noise source, use the measurement noise source to replace the calibration noise source for measurement, load the super noise ratio of the measurement noise source;

[0021] Step 7, install the mixer single sideband noise figure measurement system for measurement, control the measurement noise source to work in the source open hot state and the source off cold state respectively, obtain the linear measurement value of the hot power N RFMESH,i and the linear measurement value of the cold power N RFMESC,i of the noise figure analyzer at each measurement frequency point, determine the linear value of the cascade Y factor Y 12,i, the linear value of the cascade noise figure F 12,i , the linear value of the cascade gain-bandwidth product kGB 12,i ; error correction is performed to determine the linear value of the double-sideband conversion coefficient G 1MDSB,i and the linear value of the double-sideband noise figure F 1MDSB,i of the input filter, the measured mixer and the output filter at each measurement frequency point;

[0022] Step 8: the effects of the input filter and the output filter are removed by loss compensation to determine the linear value of the double-sideband conversion coefficient G DSB,i and the linear value of the double-sideband noise figure F DSB,i of the measured mixer at each measurement frequency point;

[0023] Step 9: the linear value of the power gain G i of each measurement frequency point is determined by using the conversion model of the double-sideband noise figure and the single-sideband noise figure of the mixer to obtain the linear value of the single-sideband conversion coefficient G SSB,i and the linear value of the single-sideband noise figure F SSB,i of the measured mixer at each measurement frequency point.

[0024] Preferably, in the step 1, if an external controlled local oscillator is required to be used when the noise figure analyzer is calibrated, a local oscillator control interface is set.

[0025] Preferably, the image rejection ratio is the difference in the amplitude of the intermediate frequency signal output by the mixer when the signals with equal amplitudes and the frequencies of the radio frequency and the image frequency are input into the input port of the mixer.

[0026] Preferably, in the step 5, the calculation formulas of the linear value of the Y factor Y 2IFCAL,i , the linear value of the local noise figure F 2IFCAL,i and the linear value of the gain-bandwidth product kGB 2IFCAL,i are as follows:

[0027]

[0028] In the formulas, Y 2IFCAL,i is the linear value of the Y factor of the noise figure analyzer at the i th measurement frequency point; N IFCALH,i is the linear measurement value of the thermal power of the noise figure analyzer at the i th measurement frequency point; N IFCALC,i is the linear measurement value of the cold power of the noise figure analyzer at the i th measurement frequency point; F 2IFCAL,i is the linear value of the local noise figure of the noise figure analyzer at the i th measurement frequency point; ENR IFCAL,i is the linear value of the noise source excess noise ratio at the i th measurement frequency point; T c is the environmental temperature, in K; T0 is the standard noise temperature, taking the value of 290 K; kGB 2IFCAL,iGain-bandwidth product linear value of the i-th measurement frequency point.

[0029] Preferably, in step 7, the calculation formula of the cascade Y-factor linear value Y 12,i , the cascade noise figure linear value F 12,i and the cascade gain-bandwidth product linear value kGB 12,i are respectively:

[0030]

[0031] In the formula, Y 12,i is the cascade Y-factor linear value of the i-th measurement frequency point; N RFMESH,i is the thermal power linear measurement value of the i-th measurement frequency point; N RFMESC,i is the cold power linear measurement value of the i-th measurement frequency point; F 12,i is the cascade noise figure linear value of the i-th measurement frequency point; ENR RF,i is the excess noise ratio linear value of the i-th measurement frequency point; kGB 12,i is the cascade gain-bandwidth product linear value of the i-th measurement frequency point.

[0032] The calculation formula of the double-sideband conversion coefficient linear value G 1MDSB,i and the double-sideband noise figure linear value F 1MDSB,i are respectively:

[0033]

[0034] In the formula, G 1MDSB,i is the double-sideband conversion coefficient linear value of the i-th measurement frequency point; F 1MDSB,i is the double-sideband noise figure linear value of the i-th measurement frequency point.

[0035] Preferably, the mixer double-sideband noise figure and single-sideband noise figure conversion model comprises a measurement noise source, an ideal amplifier and a measured mixer, and the measurement noise source, the ideal amplifier and the measured mixer are connected in sequence.

[0036] The output noise power of the measurement noise source at each measurement frequency point is determined according to the noise source excess noise ratio of the measurement noise source.

[0037] The ideal amplifier is used to describe the difference between the theoretical calculation value and the actual power value of the input noise power when the single-sideband noise figure of the measured mixer is measured; the power gain linear value of the ideal amplifier is G, which is determined according to the image rejection ratio A of the measured mixer, the excess noise ratio ENR RFdB of the measurement noise source at the radio frequency of the measured mixer and the excess noise ratio ENR IMdB of the measurement noise source at the image frequency of the measured mixer; the ideal amplifier does not generate noise, and the noise figure linear value F is 1.

[0038] The single sideband conversion coefficient of the measured mixer is F SSB , and the single sideband noise coefficient is G SSB .

[0039] The cascade characteristics of the ideal amplifier and the measured mixer correspond to the actually measured double sideband conversion coefficient F DSB and the double sideband noise coefficient G DSB .

[0040] Preferably, the power gain linear value of the ideal amplifier at each measurement frequency point is:

[0041]

[0042] In the formula, G i is the power gain linear value of the ideal amplifier at the i-th measurement frequency point; A i is the image rejection ratio of the measured mixer at the i-th measurement frequency point, in dB; ENR RFdB,i is the excess noise ratio of the measured noise source at the radio frequency of the measured mixer at the i-th measurement frequency point, in dB; ENR IMdB,i is the excess noise ratio of the measured noise source at the image frequency of the measured mixer at the i-th measurement frequency point, in dB;

[0043] The single sideband conversion coefficient linear value of the measured mixer is:

[0044]

[0045] The single sideband noise coefficient linear value of the measured mixer is:

[0046] F SSB,i =G i (F DSB,i -1)+1 (11)

[0047] In the formula, G SSB,i is the single sideband conversion coefficient linear value of the measured mixer at the i-th measurement frequency point; G DSB,i is the double sideband conversion coefficient of the measured mixer at the i-th measurement frequency point; F SSB,i is the single sideband noise coefficient linear value of the measured mixer at the i-th measurement frequency point; F DSB,i is the double sideband noise coefficient of the measured mixer at the i-th measurement frequency point.

[0048] The beneficial technical effects brought by the present application are:

[0049] (1) The noise figure analyzer based on the Y factor method at the present stage requires that the mirror frequency noise signal and various high-order harmonic mixing noise signals output by the noise source are filtered out through a filter when measuring the single sideband noise figure of the mixer. When the radio frequency and the mirror frequency of the measured mixer are close to each other, the filter cannot filter out the mirror frequency signal due to the existence of the bandwidth and the limitation of the transition band, which leads to the failure to accurately measure the single sideband noise figure of the mixer. At this time, only the double sideband noise figure can be measured, but the specific relationship equation between the double sideband noise figure and the single sideband noise figure is not given in the prior art. The present application provides a mixer single sideband noise figure measurement system and method for removing the influence of the mirror frequency. The method for accurately calculating the single sideband noise figure of the mixer by using the conversion model of the double sideband noise figure and the single sideband noise figure of the mixer is used. The mirror frequency noise signal does not need to be filtered out when measuring, and only the high-order harmonic mixing noise signal needs to be filtered out, which not only reduces the difficulty of measuring the single sideband noise figure of the mixer, but also solves the problem that the single sideband noise figure of the mixer cannot be accurately measured and evaluated due to the failure to filter out the mirror frequency noise signal.

[0050] (2) The present application provides a mixer single sideband noise figure measurement method for removing the influence of the mirror frequency. The conversion model of the double sideband noise figure and the single sideband noise figure of the mixer is used to accurately model the difference between the theoretical calculation value and the actual power value of the input noise when measuring the single sideband noise figure of the measured mixer, so as to directly use the measurement result of the double sideband noise figure of the measured mixer to accurately obtain the single sideband noise figure of the measured mixer. The single sideband noise figure of the measured mixer can also be accurately obtained when the mirror frequency noise signal cannot be filtered out. BRIEF DESCRIPTION OF DRAWINGS

[0051] Figure 1 It is a schematic diagram of the mixer single sideband noise figure measurement system for removing the influence of the mirror frequency.

[0052] Figure 2 It is a schematic diagram of the mirror frequency rejection ratio.

[0053] Figure 3 It is a schematic diagram of the noise figure analyzer calibration.

[0054] Figure 4 It is a schematic diagram of the conversion model of the double sideband noise figure and the single sideband noise figure of the mixer. DETAILED DESCRIPTION

[0055] The present application will be further described in detail below in combination with the drawings and examples.

[0056] The present application provides a mixer single sideband noise figure measurement system for removing the influence of the mirror frequency, as shown in Figure 1As shown, the mixer single sideband noise figure measurement system comprises a noise source, an input filter, a measured mixer, an output filter, a local oscillator source and a noise figure analyzer.

[0057] The noise source, the input filter, the measured mixer and the output filter are connected in sequence, wherein the noise source is a calibration noise source for calibrating the noise figure analyzer or a measurement noise source for measuring the single sideband noise figure of the mixer, the measurement noise source is connected with the input filter during measurement, the calibration noise source is connected with the noise figure analyzer during calibration, the input filter is used for filtering out the mirror frequency noise signal and various high-order harmonic mixing noise signals, and the output filter is used for filtering out the local oscillator leakage signal of the mixer and other unnecessary mixing output signals.

[0058] The noise figure analyzer is connected with the local oscillator source through a local oscillator control bus and a common time base interface, controls the frequency and power of the local oscillator source through the local oscillator control interface, and ensures that the reference frequency references of the noise figure analyzer and the local oscillator source are the same through the common time base connection.

[0059] The embodiment also provides a mixer single sideband noise figure measurement method for removing the mirror frequency influence, which adopts the mixer single sideband noise figure measurement system for removing the mirror frequency influence and comprises the following steps.

[0060] Step 1, selecting a calibration noise source to calibrate the noise figure analyzer;

[0061] The noise figure analyzer is calibrated by loading the super noise ratio of the calibration noise source, and the linear value of the super noise ratio of the calibration noise source at each measurement frequency point is determined as ENR according to the super noise ratio calibration value provided by the noise source manufacturer. IFCAL,i If an external control local oscillator needs to be used during calibration of the noise figure analyzer, the local oscillator control interface is set.

[0062] Step 2, setting a measurement mode;

[0063] The upconverter measurement mode or the downconverter measurement mode is selected according to the characteristics of the measured component, the single sideband measurement mode is set, the mode and power of the local oscillator are set, the radio frequency, the local oscillator and the intermediate frequency of the measured mixer are set, and the number of measurement frequency points and the average number of times are set.

[0064] Step 3, editing the loss characteristics of the input filter and the output filter in the noise figure analyzer.

[0065] Step 4, setting the mirror frequency rejection ratio of the measured mixer at each measurement frequency point;

[0066] The mirror frequency rejection ratio is the difference in the amplitude of the intermediate frequency signal output by the mixer when the signals with equal amplitudes and different frequencies of radio frequency and mirror frequency are input into the input port of the mixer, and the mirror frequency rejection ratio is calculated according to the following formula:Figure 2 as shown.

[0067] Step 5, connect the calibration noise source and the noise figure analyzer for calibration, as shown in Figure 3 , control the calibration noise source to work in the source open hot state and the source off cold state respectively, obtain the thermal power linear measurement value N IFCALH,i and the cold power linear measurement value N IFCALC,i of the noise figure analyzer at each measurement frequency point, determine the Y factor linear value Y 2IFCAL,i , the intrinsic noise coefficient linear value F 2IFCAL,i and the gain bandwidth product linear value kGB 2IFCAL,i of the noise figure analyzer at each measurement frequency point, wherein the calculation formulas of the Y factor linear value Y 2IFCAL,i , the intrinsic noise coefficient linear value F 2IFCAL,i and the gain bandwidth product linear value kGB 2IFCAL,i are as follows:

[0068]

[0069] In the formula, Y 2IFCAL,i is the Y factor linear value of the noise figure analyzer at the i th measurement frequency point; N IFCALH,i is the thermal power linear measurement value of the noise figure analyzer at the i th measurement frequency point; N IFCALC,i is the cold power linear measurement value of the noise figure analyzer at the i th measurement frequency point; F 2IFCAL,i is the intrinsic noise coefficient linear value of the noise figure analyzer at the i th measurement frequency point; ENR IFCAL,i is the linear value of the noise source excess noise ratio at the i th measurement frequency point; T c is the ambient temperature, in K; T0 is the standard noise temperature, taking the value of 290 K; kGB 2IFCAL,i is the gain bandwidth product linear value at the i th measurement frequency point.

[0070] Step 6, if the calibration noise source is the same as the measurement noise source, the calibration noise source is used as the measurement noise source, if the calibration noise source is different from the measurement noise source, the measurement noise source is used to replace the calibration noise source for measurement, and the excess noise ratio linear value of the noise source at the i th measurement frequency point is determined as ENR RF,i according to the excess noise ratio calibration data of the noise source, and the excess noise ratio of the measurement noise source is loaded.

[0071] Step 7, install the mixer single sideband noise figure measurement system as described above for measurement, as shown in Figure 1 , control the measurement noise source to work in the source open hot state and the source off cold state respectively, obtain the thermal power linear measurement value N RFMESH,i and the cold power linear measurement value N RFMESC,i, the linear value of the Y-factor of the cascade of the input filter, the measured mixer, the output filter and the noise figure analyzer at each measurement frequency point Y 12,i , the linear value of the noise figure of the cascade F 12,i , the linear value of the product of the gain and bandwidth of the cascade kGB 12,i are respectively:

[0072]

[0073] wherein Y 12,i is the linear value of the Y-factor of the cascade at the i-th measurement frequency point; N RFMESH,i is the linear measurement value of the hot power at the i-th measurement frequency point; N RFMESC,i is the linear measurement value of the cold power at the i-th measurement frequency point; F 12,i is the linear value of the noise figure of the cascade at the i-th measurement frequency point; ENR RF,i is the linear value of the excess noise ratio at the i-th measurement frequency point, which is determined according to the excess noise ratio calibration data of the measurement noise source; kGB 12,i is the linear value of the product of the gain and bandwidth of the cascade at the i-th measurement frequency point.

[0074] Further, error correction is performed to determine the linear value of the double-sideband conversion coefficient G 1MDSB,i and the linear value of the double-sideband noise figure F 1MDSB,i of the cascade of the input filter, the measured mixer and the output filter at each measurement frequency point.

[0075]

[0076] wherein G 1MDSB,i is the linear value of the double-sideband conversion coefficient at the i-th measurement frequency point; F 1MDSB,i is the linear value of the double-sideband noise figure at the i-th measurement frequency point.

[0077] Step 8, the influence of the input filter and the output filter is removed through loss compensation to determine the linear value of the double-sideband conversion coefficient G DSBi and the linear value of the double-sideband noise figure F DSBi of the measured mixer at each measurement frequency point.

[0078] Step 9, the linear value of the power gain G i at each measurement frequency point is determined by using the conversion model of the double-sideband noise figure and the single-sideband noise figure of the mixer, so that the linear value of the single-sideband conversion coefficient G SSBi and the linear value of the single-sideband noise figure F SSBi of the measured mixer at each measurement frequency point are obtained.

[0079] In the embodiment, the conversion model of the double-sideband noise figure and the single-sideband noise figure of the mixer is as follows: Figure 4As shown, the measurement noise source, the ideal amplifier and the measured mixer are connected in sequence, wherein the output noise power of the measurement noise source at each measurement frequency point is determined according to the noise source excess noise ratio of the measurement noise source, and the excess noise ratio value of the measurement noise source at the radio frequency of the measured mixer is set as ENR RFdB The excess noise ratio value of the measurement noise source at the image frequency of the measured mixer is ENR IMdB The ideal amplifier is used to describe the difference between the theoretical calculation value of the input noise power and the actual power value of the input noise when the measured mixer is measured for the single sideband noise figure, the power gain linear value of the ideal amplifier is G, and the single sideband noise figure linear value F of the measured mixer is determined according to the image rejection ratio A of the measured mixer, the excess noise ratio value ENR of the measurement noise source at the radio frequency of the measured mixer, the excess noise ratio value ENR of the measurement noise source at the image frequency of the measured mixer, and the noise figure linear value of the ideal amplifier is 1. RFdB IMdB The single sideband noise figure linear value F of the measured mixer is F SSB , and the single sideband conversion coefficient G is G SSB . The cascade characteristics of the ideal amplifier and the measured mixer correspond to the actual measured double sideband noise figure F DSB and the double sideband conversion coefficient G DSB .

[0080] In the embodiment, the power gain linear value of the ideal amplifier at each measurement frequency point is:

[0081]

[0082] In the formula, G i is the power gain linear value of the ideal amplifier at the i-th measurement frequency point; A i is the image rejection ratio of the measured mixer at the i-th measurement frequency point, in dB; ENR RFdB,i is the excess noise ratio of the measurement noise source at the radio frequency of the measured mixer at the i-th measurement frequency point, in dB; ENR IMdB,i is the excess noise ratio of the measurement noise source at the image frequency of the measured mixer at the i-th measurement frequency point, in dB.

[0083] Further, when the double sideband noise figure is converted to the single sideband noise figure, the single sideband conversion coefficient linear value G SSB,i and the single sideband noise figure linear value F SSB,i of the measured mixer at each measurement frequency point are:

[0084]

[0085] The single sideband noise figure linear value of the measured mixer is:

[0086] F​SSB,i =G i (F DSB,i -1)+1 (11)

[0087] In the formula, G SSB,i is the linear value of the single sideband conversion coefficient of the measured mixer at the i-th measurement frequency point; G DSB,i is the double sideband conversion coefficient of the measured mixer at the i-th measurement frequency point; F SSB,i is the linear value of the single sideband noise coefficient of the measured mixer at the i-th measurement frequency point; F DSB,i is the double sideband noise coefficient of the measured mixer at the i-th measurement frequency point.

[0088] Therefore, the difference between the theoretical calculation value of the input noise power and the actual value of the input noise power when measuring the single sideband noise coefficient of the measured mixer is used to construct a conversion model of the double sideband noise coefficient and the single sideband noise coefficient of the mixer, the input filter only needs to filter out the high harmonic mixing noise signal, and does not need to filter out the mirror frequency noise signal, and the single sideband noise coefficient of the measured mixer can be accurately obtained by directly using the measurement result of the double sideband noise coefficient of the measured mixer, the performance index requirement of the input filter is reduced, the accurate acquisition of the single sideband noise coefficient of the measured mixer is realized, and a basis for guiding the design of the mixer is provided.

[0089] In the description of the present application, it should be noted that, unless otherwise explicitly specified and limited, the terms "arrangement", "installation", "connection", "connection", "fixing" should be understood in a broad sense, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected, it can be mechanically connected, or it can be electrically connected, it can be directly connected, or indirectly connected through an intermediate medium, or it can be the communication between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0090] Of course, the above description is not a limitation of the present application, and the present application is also not limited to the above examples, and the changes, modifications, additions or replacements made by those skilled in the art within the essential scope of the present application should also be within the protection scope of the present application.

Claims

1. A mixer single sideband noise figure measurement system that removes image frequency effects, characterized by, The mixer single sideband noise figure measurement system comprises a noise source, an input filter, a measured mixer, an output filter, a local oscillator source and a noise figure analyzer; The noise source, the input filter, the measured mixer and the output filter are connected in sequence, the noise source is connected with the input filter during measurement and is connected with the noise figure analyzer during calibration; The noise figure analyzer is connected with the local oscillator source through a local oscillator control bus and a common time base interface, controls the frequency and power of the local oscillator source through the local oscillator control interface and ensures that the reference frequency bases of the noise figure analyzer and the local oscillator source are the same through the common time base connection.

2. The spurious-free mixer single-sideband noise figure measurement system of claim 1, wherein, The noise source is a calibration noise source or a measurement noise source, the calibration noise source is used for calibrating the noise figure analyzer and the measurement noise source is used for measuring the mixer single sideband noise figure.

3. A method of measuring the single sideband noise figure of a mixer free from the effects of image frequency, characterised by, The mixer single sideband noise figure measurement system for removing the mirror frequency influence comprises the following steps: Step 1, selecting a calibration noise source to calibrate the noise figure analyzer; The noise figure analyzer is calibrated by loading the calibration noise source with the excess noise ratio, and the linear value of the excess noise ratio of the calibration noise source at each measurement frequency point is determined as ENR according to the excess noise ratio scale value provided by the noise source manufacturer IFCAL,i ; Step 2, setting a measurement mode; selecting an upconverter measurement mode or a downconverter measurement mode, setting a single sideband measurement mode, setting the mode and power of the local oscillator, setting the radio frequency, the local oscillator and the intermediate frequency frequency of the measured mixer, setting the measurement frequency point number and the average number; Step 3, editing the loss characteristics of the input filter and the output filter in the noise figure analyzer; Step 4, setting the mirror frequency suppression ratio of the measured mixer at each measurement frequency point; Step 5, connect the calibration noise source and the noise figure analyzer for calibration, control the calibration noise source to work in the source open hot state and the source off cold state respectively, obtain the hot power linear measurement value N IFCALH,i and the cold power linear measurement value N IFCALC,i of the noise figure analyzer at each measurement frequency point, determine the Y factor linear value Y 2IFCAL,i , the local noise coefficient linear value F 2IFCAL,i and the gain bandwidth product linear value kGB 2IFCAL,i of the noise figure analyzer at each measurement frequency point; Step 6, if the calibration noise source is the same as the measurement noise source, the calibration noise source is used as the measurement noise source, if the calibration noise source is different from the measurement noise source, the measurement noise source is used to replace the calibration noise source for measurement and the super noise ratio of the measurement noise source is loaded; Step 7, install the mixer single sideband noise figure measurement system to measure, control the measurement noise source to work in the source open hot state and the source off cold state respectively, obtain the thermal power linear measurement value N RFMESH,i and the cold power linear measurement value N RFMESC,i of the noise figure analyzer at each measurement frequency point, determine the cascade Y factor linear value Y 12,i , the cascade noise figure linear value F 12,i , and the cascade gain bandwidth product linear value kGB 12,i of the input filter, the measured mixer, the output filter, and the noise figure analyzer at each measurement frequency point; perform error correction to determine the double sideband conversion coefficient linear value G 1MDSB,i and the double sideband noise figure linear value F 1MDSB,i of the input filter, the measured mixer, and the output filter cascade at each measurement frequency point; Step 8, remove the effect of input filter and output filter by loss compensation, determine the linear value of double sideband conversion coefficient of the measured mixer at each measurement frequency point G DSB,i and the linear value of double sideband noise coefficient F DSB,i ; Step 9, the power gain linear value G of each measuring frequency point is determined by using the double side band noise factor and single side band noise factor conversion model of the mixer i , the single side band conversion factor linear value G of the mixer of each measuring frequency point is obtained SSB,i , and the single side band noise factor linear value F SSB,i .

4. The method of spurious mixer single sideband noise figure measurement that removes mirror frequency effects of claim 3, wherein, In step 1, if an external control local oscillator is needed during calibration of the noise figure analyzer, the local oscillator control interface is set.

5. The method of spurious mixer single sideband noise figure measurement that removes mirror frequency effects of claim 3, wherein, The mirror frequency suppression ratio is the difference between the amplitudes of the intermediate frequency signals output by the mixer when the signals with equal amplitudes and the frequencies of radio frequency and mirror frequency are input into the input port of the mixer.

6. The method of spurious mixer noise figure measurement of a single sideband with mirror frequency rejection of claim 3, wherein, The calculation formula of the Y factor linear value Y 2IFCAL,i , the local noise figure linear value F 2IFCAL,i , and the gain-bandwidth product linear value kGB 2IFCAL,i in step 5 is respectively: In the formula, Y 2IFCAL,i is the linear value of the noise figure analyzer at the i-th measurement frequency; N IFCALH,i is the linear measurement value of the thermal power of the noise figure analyzer at the i-th measurement frequency; N IFCALC,i is the linear measurement value of the cold power of the noise figure analyzer at the i-th measurement frequency; F 2IFCAL,i is the linear value of the noise figure analyzer at the i-th measurement frequency; ENR IFCAL,i is the linear value of the noise source excess noise ratio at the i-th measurement frequency; T c is the ambient temperature, in K; T0 is the standard noise temperature, taking the value of 290 K; kGB 2IFCAL,i is the linear value of the gain-bandwidth product at the i-th measurement frequency.

7. The method of spurious mixer noise figure measurement of a single sideband with mirror frequency rejection of claim 6, wherein, The calculation formula of the cascade Y factor linear value Y 12,i , the cascade noise figure linear value F 12,i and the cascade gain-bandwidth product linear value kGB 12,i in step 7 is respectively: where Y 12,i is the linear value of the cascade Y-factor for the i-th measurement frequency point; N RFMESH,i is the linear measurement of the hot power for the i-th measurement frequency point; N RFMESC,i is the linear measurement of the cold power for the i-th measurement frequency point; F 12,i is the linear value of the cascade noise figure for the i-th measurement frequency point; ENR RF,i is the linear value of the excess noise ratio for the i-th measurement frequency point; kGB 12,i is the linear value of the cascade gain-bandwidth product for the i-th measurement frequency point. The double side band frequency conversion coefficient linear value G 1MDSB,i And the double side band noise coefficient linear value F 1MDSB,i The calculation formula is respectively: In the formula, G 1MDSB,i is the linear value of the double sideband conversion coefficient of the ith measurement frequency point; F 1MDSB,i is the linear value of the double sideband noise coefficient of the ith measurement frequency point.

8. The method of spurious mixer single sideband noise figure measurement that removes mirror frequency effects of claim 7, wherein, The mixer double sideband noise figure and single sideband noise figure conversion model comprises a measurement noise source, an ideal amplifier and a measured mixer, and the measurement noise source, the ideal amplifier and the measured mixer are connected in sequence; The output noise power of the measurement noise source at each measurement frequency point is determined according to the noise source super noise ratio of the measurement noise source; The ideal amplifier is used to describe the difference between the theoretical calculated value of input noise power and the actual value of input noise power when measuring the single sideband noise figure of the measured mixer; the linear value of power gain of the ideal amplifier is G, and the linear value of noise figure of the ideal amplifier is F RFdB The linear value of noise figure of the ideal amplifier is F, and the linear value of power gain of the ideal amplifier is G IMdB The linear value of noise figure of the ideal amplifier is F, and the linear value of power gain of the ideal amplifier is G The single sideband noise figure of the measured mixer is F SSB The single sideband conversion figure is G SSB ​ The cascade properties of the ideal amplifier and the measured mixer correspond to the actual measured double sideband noise figure F DSB and double sideband conversion gain G DSB .

9. The method of spurious mixer single sideband noise figure measurement that removes mirror frequency effects of claim 8, wherein, The power gain linear value of the ideal amplifier at each measurement frequency point is: In the formula, G i is the power gain linear value of the ideal amplifier at the i-th measurement frequency point; A i is the image rejection ratio of the measured mixer at the i-th measurement frequency point, in dB; ENR RFdB,i is the excess noise ratio of the measured noise source at the i-th measurement frequency point at the radio frequency of the measured mixer, in dB; ENR IMdB,i is the excess noise ratio of the measured noise source at the i-th measurement frequency point at the image frequency of the measured mixer, in dB; The single sideband conversion coefficient linear value of the measured mixer is: The single sideband noise figure linear value of the measured mixer is: F SSB,i = G i (F DSB,i -1)+1 (11) In the formula, G SSB,i is the linear value of the single sideband conversion coefficient of the measured mixer at the ith measurement frequency point; G DSB,i is the double sideband conversion coefficient of the measured mixer at the ith measurement frequency point; F SSB,i SIBNlinear(i) is the linear value of the single sideband noise figure of the measured mixer at the i-th measurement frequency point; F DSB,i is the double sideband noise figure of the measured mixer at the i-th measurement frequency point.

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