Y factor method and cold source method integrated noise coefficient measuring instrument and method

Abstract

The invention discloses a noise coefficient measuring instrument and method comprehensively integrating a Y factor method and a cold source method, and belongs to the technical field of microwave and millimeter wave testing. The instrument hardware integrates S parameter measuring equipment, a high-sensitivity noise receiver, an impedance tuner, a noise source driving circuit and a low-loss high-isolation switch assembly. Through switching of the switch assembly, a measurement path is reconstructed, and fusion of two measurement modes of a Y factor method and a cold source method is realized on the same instrument. According to the cold source method mode, through impedance allocation and vector error calibration, the measurement error of a tool clamp in a non-ideal matching scene such as a chip is overcome; the Y factor method mode is directly connected with a tested piece through a calibrated noise source, and rapid and high-precision measurement is provided for coaxial interconnection testing. The problem of measurement limitation of a single method is solved, the requirement for high-precision noise coefficient measurement in a complex test environment can be met through a single machine, and the measurement efficiency and the application range are remarkably improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of microwave and millimeter wave testing, and particularly relates to a Y-factor method and cold source method integrated noise figure measurement instrument and method. BACKGROUND

[0002] Noise figure analyzer is an important professional testing instrument for characterizing the noise performance of devices and systems. Noise figure measurement is a key link in research and development and process verification in manufacturing industry. High-precision noise figure measurement not only can accelerate the design and verification speed, but also directly determines the product development cycle and application effectiveness.

[0003] Currently, noise figure measurement and analysis mainly have two forms of Y-factor method and cold source method, which correspond to two different instrument products respectively.

[0004] The most similar existing implementation scheme to the present application mainly has Y-factor method and cold source method.

[0005] (1) Y-factor method, also known as cold / hot noise source method, is the most commonly used noise figure measurement method. Its theoretical basis relies on the noise power linearity of linear two-port network, that is, the output noise and input noise power (temperature) of the measured device are in linear relationship, as shown in formula (1). Figure 1

[0006] This method needs a precisely calibrated noise source as a noise power standard. The noise source works in two states of on and off. The noise figure tester controls the on and off states of the noise source to obtain the corresponding thermal power P hot and cold power P cold .

[0007] The ratio of thermal power P hot to cold power P cold is defined as Y-factor. The equivalent input noise temperature of the measured device can be calculated through Y-factor measurement, and then the noise figure of the measured device can be calculated according to the relationship between the equivalent input noise temperature and the noise figure, as shown in formulas (1), (2) and (3).

[0008] (1); (2); (3); In the formulas, T h is the equivalent output noise temperature when the noise source is on; T e is the equivalent input noise temperature of the measured device, T c is the equivalent output noise temperature when the noise source is off, usually referred to as normal temperature, F is the noise figure, T0 is the standard noise temperature 290K, and ENR is the noise source excess noise ratio.

[0009] ​(ii) Cold Source Method. The theoretical basis of this method is the same as the Y-factor method, both of which rely on the linearity of the noise power of a linear two-port network, i.e., the output noise and input noise power (temperature) of the device under test are linearly related. Compared with the Y-factor method, which determines a straight line according to the principle of two points, the cold source method noise factor measurement principle is that the slope and a reference point are known, and then the additional noise power of the device under test can be obtained, and the noise factor can be calculated, as shown in Equation (2). Figure 2

[0010] In the cold source method noise factor measurement, a noise source does not need to be connected to the input end of the device under test (DUT), only a known load (usually 50 Ω) is needed, which is equivalent to the Y-factor method noise source working in the source-off state (also called cold state), so it is called the cold source method. This method needs to measure the gain of the DUT separately.

[0011] The noise factor is usually measured in a 50-Ω source impedance environment, but in fact the noise factor of a device under test will change with the change of the source impedance presented at the input end of the device under test, and this change is characterized by noise parameters, as shown in Equation (4).

[0012] (4); In the formula: is the noise factor, is the minimum noise factor, is the equivalent input noise resistance, is the 50-Ω characteristic impedance, is the source reflection coefficient, is the optimum reflection coefficient, where , and (including amplitude and phase) are usually referred to as amplifier noise parameters.

[0013] As can be seen from Equation (4), if at least four different source impedance states are presented at the input port of the device under test, the corresponding noise factors are tested, and the corresponding test equations are formed into an equation set, the noise parameters can be solved. The cold source method uses an impedance tuner to change the source matching around 50 Ω, and by obtaining the noise factors under different impedances and the vector error model, the noise factor under the 50-Ω impedance condition can be accurately calculated. Since noise measurement is very sensitive, more than four impedance states are often measured in practice, and then the least squares algorithm is used to improve the measurement accuracy.

[0014] This method can eliminate the mismatch introduced by the source end, test fixtures and probes, and can also eliminate the error caused by the noise parameter effect of the noise receiver itself. For tooling fixtures, on-chip and ATE (non-50-Ω characteristic impedance) applications, the measurement accuracy is higher than that of the traditional Y-factor method noise factor tester. ​

[0015] The main shortcomings of the two closest prior art implementations to the present invention are: 1) Noise figure measurement by Y-factor method, which assumes that the DUT and the system are ideally matched. For fixture, DUT and ATE applications, the noise source cannot be directly connected to the DUT, and there is a large measurement uncertainty due to mismatch error and noise parameter effects.

[0016] 2) Noise figure measurement by cold source method, which requires full two-port calibration using a calibration device, impedance matching using an impedance tuner, and noise receiver calibration using a noise source. The main disadvantage of this method is that for coaxial interconnection testing, the test accuracy is basically the same as the Y-factor method, but it requires more calibration accessories, the calibration process is complicated, the professional skills of the operator are required, and the test cost is high.

[0017] Therefore, there is an urgent need in the art for an instrument and method that can integrate the advantages of the two methods and provide a comprehensive, high-precision, flexible noise figure measurement solution. SUMMARY

[0018] To solve the above technical problems in the prior art, the present invention proposes a Y-factor method and cold source method integrated noise figure measurement instrument and method, which is reasonable in design, overcomes the shortcomings of the prior art, and has good effects.

[0019] To achieve the above purpose, the present invention adopts the following technical solutions: A Y-factor method and cold source method integrated noise figure measurement instrument, comprising: an S-parameter measurement device configured to measure the S-parameters of a DUT; a noise receiver configured to measure the noise power; an impedance tuner configured to change the source impedance presented to the DUT; a noise source drive circuit configured to drive and control an external noise source; a switch assembly configured to connect the ports of the S-parameter measurement device, the noise receiver, the impedance tuner and the noise source drive circuit in different ways by switching the connection state of its internal channels to form a first connection topology for performing cold source method measurement and a second connection topology for performing Y-factor method measurement, respectively.

[0020] Preferably, the first connection topology is a cold source method measurement topology, and the connection relationship is: the output end of the impedance tuner is connected to the input end of the DUT through a switch channel; the first port of the S-parameter measurement device is connected to the input end of the impedance tuner through a switch channel; The second port of the S parameter measurement device and the input end of the noise receiver are connected to the output end of the device under test through a switch channel.

[0021] Preferably, the second connection topology is a Y-factor measurement topology, and the connection relationship is as follows: The noise source driving circuit is connected to an external noise source through a switch channel, and the external noise source is directly connected to the input end of the device under test. The input end of the noise receiver is connected to the output end of the device under test through a switch channel.

[0022] In addition, the application also mentions a Y-factor and cold source integrated noise figure measurement method, which uses a Y-factor and cold source integrated noise figure measurement instrument as described above, including a cold source measurement mode and a Y-factor measurement mode, and the instrument selects between the two modes through switching of internal switch channels.

[0023] Preferably, the cold source measurement mode includes the following steps: Calibration step: Step S01: full two-port S parameter calibration is performed to eliminate errors introduced by mismatch errors and noise parameter effects; Step S02: noise receiver calibration, combined with a noise source and an impedance tuner, measures corresponding noise powers under multiple different source impedance states, and calculates noise parameters of the noise receiver based on a noise parameter model formula; Measurement step: Step S03: S parameter measurement: using an S parameter measurement device and an impedance tuner, S parameters of the device under test and S parameters of the impedance tuner are measured; Step S04: noise parameter measurement: under multiple sets of impedance states provided by the impedance tuner, total noise powers of the device under test and the noise receiver in cascade are measured; Step S05: multiple source impedance states and corresponding cascade noise figure values are substituted into a noise parameter model to solve the equation set, and total noise parameters and gains after the device under test and the noise receiver are in cascade are obtained; Step S06: according to the total noise parameters and the gains, noise parameters of the device under test are calculated.

[0024] Preferably, the Y-factor measurement mode includes the following steps: Noise receiver calibration, specifically including the following steps: Step S07: the noise source is directly connected to the noise receiver through a switch channel; Step S08: the hot and cold noise powers of the noise receiver channel under two states of the noise source being on and off are measured, denoted as P 2hot and P 2cold ; Step S09: based on P 2hot and P 2cold , calculate the noise figure F2 of the noise receiver; The measured piece measurement, specifically comprising the following steps: Step S10: connect the noise source to the input end of the measured piece, and connect the output end of the measured piece to the noise receiver through the switch channel; Step S11: measure the hot and cold noise power of the measured piece and the noise receiver in series under the on and off states of the noise source, denoted as P 12hot and P 12cold ; Step S12: based on P 12hot and P 12cold , calculate the noise figure of the measured piece and the noise receiver in series, denoted as F 12 ; Step S13: according to formulas (5) and (6), calculate the gain G DUT and the noise figure F DUT of the measured piece; (5); (6).

[0025] Preferably, the noise parameter model formula is as follows: (4); In the formula: is the noise figure, is the minimum noise figure, is the equivalent input noise resistance, is the 50Ω characteristic impedance, is the source reflection coefficient, is the optimum reflection coefficient, wherein, , and (including amplitude and phase) are commonly referred to as amplifier noise parameters.

[0026] The beneficial technical effects brought by the present application are: 1. Comprehensive function: a single instrument integrates two mainstream measurement methods, users do not need to purchase two special instruments, reducing the purchase cost.

[0027] 2. Optimal precision: select the optimal method for different application scenarios-Y factor method for coaxial test, cold source method for chip / fixture test, to ensure the highest precision of measurement results in various environments.

[0028] 3. High flexibility: switch by software control, measurement mode conversion is fast and convenient, greatly improving the test efficiency.

[0029] 4. Easy to use: Although the internal complexity, but provides a simple operation interface for the user. Y-factor method mode maintains its inherent ease of operation; complex calibration process of cold source method mode can be guided by instrument software to complete, reducing the professional requirements for the operator.

[0030] Two methods of functional performance complementarity, synergy is significant, both can solve the Y-factor method in the fixture, in the piece and ATE application in the presence of measurement accuracy problem, but also can solve the cold source method in the coaxial interconnection measurement when there are many calibration kits, calibration process is cumbersome, the professional ability of the operator is required, the test cost is high. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 Y-factor method noise figure theory principle diagram for prior art.

[0032] Figure 2 Cold source method noise figure measurement theory diagram.

[0033] Figure 3 The overall flow chart of the measurement method of the present application. DETAILED DESCRIPTION

[0034] The present application will be further described in detail below in conjunction with the drawings and specific embodiments: The Y-factor method and cold source method integrated instrument hardware implementation scheme as shown in Figure 3 The main includes S parameter measurement equipment, high sensitivity noise receiver, impedance matching device, noise source drive circuit and low loss high isolation switch component, realizes Y factor method and cold source method two form instrument hardware integration and single instrument two test method fusion problem.

[0035] Example one: cold source method noise figure measurement; When the cold source method mode is selected, the switch channel is connected as follows: 1) Noise power measurement configuration When measuring the noise power, the internal source of port 1 is closed, the internal switch K1 is disconnected from the output of port 1 source and the measured piece, the impedance matching device is connected to the instrument through the switch K1, and the input end of the measured piece (DUT) is connected.

[0036] At least four different source impedance states are presented at the input port of the measured piece using the impedance matching device, and the noise receiver measures the noise power output by the measured piece.

[0037] 2) S parameter measurement, source output at port 1 When S parameter measurement is performed with source output at port 1, the impedance tuner is in pass-through state, the source signal at port 1 is input to the port 1 of the DUT through switch K1 and the impedance tuner, the input port of the noise receiver is terminated by the internal load through switch K2, and the source output signal at port 2 of the DUT is absorbed by the load connected to the port 2 source output through switch K2 and the port 2 reference coupler.

[0038] 3) S parameter measurement, source output at port 2 When S parameter measurement is performed with source output at port 2, the impedance tuner is in pass-through state, the source signal at port 2 is input to the port 2 of the DUT through the internal switch of the noise receiver and switch K2 of the source / noise input port, the source output signal at port 2 of the DUT is absorbed by the load connected to the port 2 source output through switch K1 and the impedance tuner.

[0039] The measurement process is as follows: mainly including two steps of calibration and measurement.

[0040] First, calibration is performed to determine all system errors, mainly including: (1) full two-port S parameter calibration to eliminate errors introduced by noise figure measurement mismatch error and noise parameter effect; (2) noise receiver calibration to obtain the secondly corrected noise figure measurement result.

[0041] During calibration, the noise source is combined and the power in several impedance states is measured through the source impedance tuner, and the noise figure, noise parameter and gain values of the noise receiver can be obtained through the calculation of formula (4).

[0042] The measurement mainly includes: connecting the DUT; (1) S parameter measurement, including S parameter measurement of the DUT and S parameter measurement of the impedance tuner.

[0043] (2) noise parameter measurement. After calibration, when the DUT is measured, the total noise power of the DUT and the noise figure receiver in cascade is measured in several impedance states, the values of multiple source impedance-noise figure pairs are brought into formula (4) to form an equation group, so as to obtain the total noise figure, noise parameter and total gain of the DUT and the receiver, and finally the noise parameter of the DUT is calculated through mathematical operation.

[0044] The cold source method can overcome the challenge of accurate noise figure measurement under the environment of tooling fixture, on-chip and ATE by combining the unique source matching error calibration method and vector error calibration technology, and can obtain high-precision noise figure measurement results.

[0045] Example two: Y factor method noise figure measurement When the Y factor method mode is selected, the switch channel switching path is as follows: The external noise source is directly connected to the input of the DUT.

[0046] The output of the DUT is connected to "port 2" of the instrument, which is directly connected to the input of the noise receiver through switch K2 (the relevant path of the S-parameter measurement device is disconnected).

[0047] The measurement process is as follows: The Y-factor method measurement includes two steps of calibration and measurement.

[0048] 1. First, the noise receiver calibration is performed. The same noise source is directly connected to port 2 of the instrument, and the noise source is connected to the noise receiver through the internal switch K2 of the instrument, the hot and cold noise powers of the noise receiver channel in the on and off states of the noise source are measured, and are denoted as P 2hot and P 2cold , the noise figure of the noise receiver is calculated, and is denoted as F2.

[0049] 2. Then, the measurement is performed by connecting the measured member. The noise source is removed from port 2 of the instrument, the noise source input is connected to the input port of the measured member, and the output of the measured member is connected to port 2, the hot and cold noise powers of the measured member and the noise receiver in the on and off states of the noise source are measured, and are denoted as P 12hot and P 12cold , the noise figure of the measured member and the noise receiver is calculated, and is denoted as F 12 .

[0050] The gain (G DUT ) and the noise figure (F DUT ) of the measured member are calculated according to formulas (5) and (6).

[0051] (5) ; (6) ; The relative power accuracy of the noise power detector is very important when the Y-factor is tested in the hot and cold noise power test, and the absolute power accuracy is not very important, because the Y-factor method is a ratio measurement method. The Y-factor method calibration and measurement process is simple and easy to use, and the measurement accuracy is very high, especially when the noise source has good output matching (50Ω characteristic impedance) and can be directly connected to the measured member.

[0052] The present application proposes a kind of Y factor method and cold source method two kinds of instruments comprehensive integration to a kind of instrument, realize the fusion problem of two kinds of test methods of single instrument, give full play to the advantages and characteristics of two kinds of measurement methods, solve different impedance state noise figure measurement problem, realize the promotion of noise figure measurement precision and measurement capacity.

[0053] Of course, the above description is not a limitation of the present application, and the present application is not limited to the above examples. Changes, modifications, additions or substitutions made by those skilled in the art within the spirit and scope of the present application should also be included in the protection scope of the present application.

Claims

1. A noise figure measuring instrument integrating the Y-factor method and the cold source method, characterized in that, include: S-parameter measuring equipment, configured to measure the S-parameters of the test piece; A noise receiver is configured to measure noise power; An impedance tuner is configured to change the source impedance presented to the device under test. A noise source drive circuit is configured to drive and control an external noise source; The switching assembly is configured to connect the ports of the S-parameter measurement device, the noise receiver, the impedance tuner, and the noise source drive circuit in different ways by switching the connection state of its internal channels, to respectively form a first connection topology for performing cold source method measurements and a second connection topology for performing Y-factor method measurements.

2. The noise figure measuring instrument integrating the Y-factor method and the cold source method according to claim 1, characterized in that, The first connection topology is the cold source method measurement topology, and its connection relationship is as follows: The output of the impedance tuner is connected to the input of the device under test via a switching channel; The first port of the S-parameter measurement device is connected to the input of the impedance modulator via a switch channel; The second port of the S-parameter measuring device and the input of the noise receiver are connected to the output of the device under test via a switch channel.

3. The noise figure measuring instrument integrating the Y-factor method and the cold source method according to claim 1, characterized in that, The second connection topology is the Y-factor method measurement topology, and its connection relationship is as follows: The noise source drive circuit is connected to an external noise source through a switching channel, which is directly connected to the input terminal of the device under test. The input of the noise receiver is connected to the output of the device under test via a switch channel.

4. A noise figure measurement method integrating the Y-factor method and the cold source method, characterized in that, Using as claimed in the claims The noise figure measuring instrument that integrates the Y-factor method and the cold source method as described in 1 includes a cold source method measurement mode and a Y-factor method measurement mode. The instrument can select between the two modes by switching the internal switching channel.

5. The noise figure measurement method integrating the Y-factor method and the cold source method according to claim 4, characterized in that, The cold source method measurement mode includes the following steps: Calibration steps: Step S01: Perform full two-port S-parameter calibration to eliminate errors introduced by mismatch and noise parameter effects; Step S02: Perform noise receiver calibration. Combine the noise source and impedance matcher, measure the corresponding noise power under multiple different source impedance states, and calculate the noise parameters of the noise receiver based on the noise parameter model formula. Measurement steps: Step S03: S-parameter measurement: Using an S-parameter measurement device and an impedance tuner, measure the S-parameters of the device under test and the S-parameters of the impedance tuner. Step S04: Noise parameter measurement: Under the multiple impedance conditions provided by the impedance tuner, measure the total noise power of the device under test and the cascaded noise receiver. Step S05: Substitute the multiple source impedance states and their corresponding cascaded noise figure values ​​into the noise parameter model, solve the equation set, and obtain the total noise parameters and gain after the device under test and the noise receiver are cascaded. Step S06: Calculate the noise parameters of the device under test based on the total noise parameters and the gain.

6. The noise figure measurement method integrating the Y-factor method and the cold source method according to claim 4, characterized in that, The Y-factor method measurement mode includes the following steps: Noise receiver calibration specifically includes the following steps: Step S07: Connect the noise source directly to the noise receiver via the switch channel; Step S08: Measure the thermal and cold noise power of the noise receiver channel when the noise source is on and off, and record it as P. 2hot and P 2cold ; Step S09: Based on P 2hot and P 2cold Calculate the noise figure F2 of the noise receiver; The measurement of the test piece includes the following steps: Step S10: Connect the noise source to the input terminal of the device under test, and connect the output terminal of the device under test to the noise receiver through the switching channel; Step S11: Measure the thermal and cold noise power of the device under test and the noise receiver cascaded together, with the noise source in both on and off states, and record it as P. 12hot and P 12cold ; Step S12: Based on P 12hot and P 12cold Calculate the noise figure of the cascaded device under test and noise receiver, denoted as F. 12 ; Step S13: Calculate the gain G of the device under test according to formulas (5) and (6). DUT and noise figure F DUT ; （5）； （6）。 7. The noise figure measurement method integrating the Y-factor method and the cold source method according to claim 5, characterized in that, The formula for the noise parameter model is shown below: （4）； In the formula: Noise figure To achieve the minimum noise figure, It is the equivalent input noise resistance. It is the optimal reflectance coefficient. It is the source reflection coefficient. It is the characteristic impedance.

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