A method to extend the range of noise figure measurement

Abstract

The present invention discloses a method for extending the noise figure measurement range, belonging to the technical field of noise figure measurement. By adopting a noise source, a noise figure tester and a low-noise amplifier (hereinafter referred to as LNA), the noise figure measurement range of the existing technical solution is extended, and accurate measurement of a device under test with a noise figure greater than 30dB is achieved. The present invention is proposed in light of the demand background of domestic large noise figure measurement technology, solves the technical bottleneck of the existing technical solution in large noise figure measurement, meets the demand for accurate measurement of large noise figure indicators in test scenarios such as power amplifiers and automatic test systems, and will greatly expand the application range of Y-factor method noise figure testers.

Description

Technical Field

[0001] The invention belongs to the technical field of noise figure measurement, and in particular relates to a method for extending the noise figure measurement range. Background Art

[0002] Noise figure is a measure of the degradation of the signal-to-noise ratio (SNR) of a linear network to the transmitted signal. It is defined as the ratio of the SNR at the network input to the SNR at the output, when the network input is held at a standard noise temperature of 290K. Currently, there are two primary methods for measuring noise figure. The most commonly used is the Y-factor method, which uses a noise source to provide two known, stable input noise levels. This method is easy to use and offers high accuracy, especially when the noise source has a good output match and can be directly connected to the input port of the device under test. Both signal / spectrum analyzer-based noise figure measurement options and dedicated noise figure analyzers employ the Y-factor method. Another method, the cold-source method, is based on a vector network analyzer. Instead of using a noise source, a source impedance tuner is used to change the source impedance during the noise figure measurement, effectively creating a source impedance pull technique. The cold-source method achieves the highest noise figure measurement accuracy in the industry by combining vector error correction with a unique source calibration technique.

[0003] The most similar existing implementation scheme to the present invention is the Y-factor method, whose measurement principle is based on the cascade formula of the noise coefficient of the linear network. Figure 1 As shown:

[0004] The Y-factor noise figure tester (hereinafter referred to as the noise figure tester) measures the noise figure of the device under test, which is equivalent to the device under test and the noise figure tester in cascade: the device under test is the first stage and the noise figure tester is the second stage. Note: the noise figure of the device under test is F1, the gain is G1, the noise figure of the noise figure tester is F2, and the noise figure of the cascade of the device under test and the noise figure tester is F 12 The noise figure cascade formula of the two-stage network of the device under test and the noise figure tester is:

[0005]

[0006] The implementation scheme mainly includes two steps: calibration and measurement.

[0007] 1) Calibration

[0008] Connect the noise source output directly to the input port of the noise figure meter, such as Figure 2 As shown, the noise figure F2 of the noise figure tester is measured, and the hot and cold noise powers in the two states of the noise source on and off are stored, recorded as N 2hot 、N 2cold ;

[0009] 2) Measurement

[0010] After calibration is completed, connect the device under test, such as Figure 1 As shown, the cascade noise figure F of the device under test and the noise figure tester is measured. 12 , and store the hot and cold noise power in the two states of the noise source on and off, recorded as N 12hot 、N 12cold .

[0011] The noise figure tester automatically calculates and displays the gain and noise figure of the device under test. The calculation formula is as follows:

[0012]

[0013]

[0014] The main disadvantage of the existing implementation scheme that is closest to the present invention is that it is limited by the size of the noise coefficient of the current commercial noise source, and cannot accurately measure the test piece with a noise coefficient greater than 30dB. The reasons are analyzed as follows: The Y-factor method for noise coefficient measurement generally requires that the lower limit of the Y-factor linear value is 1.1. The smaller the Y factor, the closer the hot and cold noise powers are, the greater the quantization error of the noise coefficient tester for the noise power, and the lower the noise coefficient measurement accuracy. The nominal values ​​of the current commercial noise source's noise coefficient are generally 5dB / 15dB / 20dB. The larger the noise coefficient, the larger the noise coefficient measurement range. Using a noise source with a nominal value of 20dB, when the ambient temperature is equal to 290K, the maximum measurable noise coefficient is 30dB.

[0015] F max =ENR-10lg(Y-1)=20-10lg(1.1-1)=30dB (4). Summary of the Invention

[0016] In view of the above technical problems existing in the prior art, the present invention proposes a method for expanding the noise figure measurement range, which has a reasonable design, overcomes the shortcomings of the prior art, and has good effects.

[0017] In order to achieve the above object, the present invention adopts the following technical solutions:

[0018] A method for extending the noise figure measurement range uses a noise source, a noise figure meter, and a low noise amplifier (LNA). When measuring the noise figure of a device under test, the LNA serves as the first stage, the device under test serves as the second stage, and the noise figure meter serves as the third stage. Note: the noise figure of the LNA is F1', and the gain is G'1; the noise figure of the device under test is F'2, and the gain is G'2; the noise figure of the noise figure meter is F3; and the noise figure of the cascaded network of the LNA and the device under test is F' 12 , the gain is G' 12The noise figure of the three-stage cascade network of LNA, DUT and noise figure tester is F 123 , the gain is G 123 ;

[0019] Step 1: Calibrate the noise figure meter;

[0020] Step 2: Measure the noise figure F' of the cascaded LNA and DUT 12 and gain G' 12 ;

[0021] Step 3: Measure the LNA's noise figure F1' and gain G'1;

[0022] Step 4: Calculate the noise figure F'2 and gain G'2 of the DUT.

[0023] Preferably, step 1 specifically includes the following steps:

[0024] Step 1.1: Connect the output of the noise source directly to the input of the noise figure meter.

[0025] Step 1.2: Measure the noise figure F3 of the noise figure meter and store the hot and cold noise power of the noise source in the on and off states, recorded as N 3hot 、N 3cold .

[0026] Preferably, step 2 specifically includes the following steps:

[0027] Step 2.1: Connect the noise source to the input port of the LNA. Connect the output of the LNA and the DUT to the input port of the noise figure meter after cascading.

[0028] Step 2.2: Measure the noise figure F of the three-stage cascade network of LNA, DUT, and noise figure meter 123 , and store the hot and cold noise power of the noise source in the on and off states, recorded as N 123hot 、N 123cold ;

[0029] Step 2.3: The noise figure meter automatically calculates and displays the cascaded gain G' of the LNA and the DUT. 12 and noise figure F' 12 , the calculation formula is as follows:

[0030]

[0031]

[0032] Preferably, step 3 specifically includes the following steps:

[0033] Step 3.1: Connect the noise source to the input port of the LNA and the output of the LNA to the input port of the noise figure meter.

[0034] Step 3.2: Measure the noise figure of the cascaded LNA and noise figure meter, recorded as F' 13 , and store the hot and cold noise power of the noise source in the on and off states, recorded as N' 13hot 、N' 13cold ;

[0035] Step 3.3: The noise figure meter automatically calculates and displays the LNA's gain G'1 and noise figure F1'. The calculation formula is as follows:

[0036]

[0037]

[0038] Preferably, step 4 specifically includes the following steps:

[0039] Step 4.1: The cascaded noise figure formula of the LNA and the device under test is:

[0040]

[0041] Step 4.2: Substitute the noise figure F' measured in step 2.3 12 Substitute the gain G'1 and noise figure F1' measured in step 3.3 into formula (9) to calculate the noise figure F'2 of the device under test:

[0042] F'2=(F' 12 -F'1)×G'1+1 (10);

[0043] Step 4.3: Gain G' measured according to step 2.3 12 The gain G'2 of the DUT is calculated using the gain G'1 measured in step 3.3:

[0044]

[0045] The beneficial technical effects brought about by the present invention are:

[0046] The present invention expands the noise figure measurement range of the prior art solution and realizes accurate measurement of a noise figure greater than 30 dB.

[0047] The present invention is proposed in light of the demand for domestic large noise figure measurement technology, and solves the technical bottleneck of existing technical solutions in large noise figure measurement, and meets the demand for accurate measurement of large noise figure indicators in test scenarios such as power amplifiers and automatic test systems. It will greatly expand the application scope of Y-factor noise figure testers. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 A connection diagram for noise figure measurement of a conventional technology solution;

[0049] Figure 2 This is the connection diagram for calibration;

[0050] Figure 3 This is a connection diagram for measuring the noise figure and gain of the cascaded LNA and DUT.

[0051] Figure 4 This is the connection diagram for measuring the noise figure and gain of the LNA. DETAILED DESCRIPTION

[0052] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0053] The measurement principle of the present invention is the same as that of the existing technical solution, and there are innovative breakthroughs in the technical solution composition and measurement method. The technical implementation of the present invention requires additional configuration of LNA, and the measurement connection frame is as follows Figure 3 As shown, the LNA is the first stage, the DUT is the second stage, and the noise figure meter is the third stage. Note: The noise figure of the LNA is F1', and the gain is G'1; the noise figure of the DUT is F'2, and the gain is G'2; the noise figure of the noise figure meter is F3; the noise figure of the cascaded network of the LNA and DUT is F' 12 , the gain is G' 12 The noise figure of the three-stage cascade network of LNA, DUT and noise figure tester is F 123 , the gain is G 123 .

[0054] The testing steps of the present invention are as follows:

[0055] Step 1: Calibrate the Noise Figure Meter

[0056] Connect the noise source output directly to the input port of the noise figure meter, such as Figure 2 As shown, the noise figure F3 of the noise figure tester is measured, and the hot and cold noise powers in the two states of the noise source on and off are stored, recorded as N 3hot 、N 3cold ;

[0057] Step 2: Measure the noise figure and gain of the cascaded LNA and DUT

[0058] After calibration is completed, Figure 3 The test system is connected as shown to measure the noise figure F of the three-stage cascade network of LNA, DUT and noise figure tester. 123, and store the hot and cold noise power in the two states of the noise source on and off, recorded as N 123hot 、N 123cold .

[0059] The noise figure tester automatically calculates and displays the cascaded gain G' of the LNA and the device under test. 12 and noise figure F' 12 , the calculation formula is as follows:

[0060]

[0061]

[0062] Step 3: Measure the LNA's noise figure and gain

[0063] Test the connection as Figure 4 As shown, the cascade noise figure of the LNA and the noise figure tester is measured and recorded as F' 13 , and store the hot and cold noise power in the two states of the noise source on and off, recorded as N' 13hot 、N' 13cold .

[0064] The noise figure meter automatically calculates and displays the LNA's gain G'1 and noise figure F1'. The calculation formula is as follows:

[0065]

[0066]

[0067] Step 4: Calculate the DUT’s noise figure and gain

[0068] The cascaded noise figure formula of the LNA and the device under test is:

[0069]

[0070] The noise figure F' measured in step 2) 12 Substituting the gain G'1 and noise figure F1' measured in step 3) into formula (9), the noise figure F'2 of the device under test can be calculated:

[0071] F'2=(F' 12 -F1')×G'1+1 (10)

[0072] According to the gain G' measured in step 2) 12 The gain G'2 of the DUT can be calculated using the gain G'1 measured in step 3):

[0073]

[0074] The present invention configures an LNA and optimizes the compromise between its core indicators such as gain, noise figure and input matching, thereby reducing the noise figure of the cascaded LNA and the device under test to within the accurate measurement range of the noise figure tester without worsening the system mismatch error.

[0075] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the essential scope of the present invention should also fall within the scope of protection of the present invention.

Claims

1. A method for extending the noise figure measurement range, characterized by: When measuring the noise figure of a device under test using a noise source, a noise figure meter, and a low-noise amplifier, the low-noise amplifier serves as the first stage, the device under test as the second stage, and the noise figure meter as the third stage. Note: The noise figure of the low-noise amplifier is F1', and the gain is G1'; the noise figure of the device under test is F'2, and the gain is G'2; the noise figure of the noise figure meter is F3; and the noise figure of the two-stage network cascade of the low-noise amplifier and the device under test is F' 12 , the gain is G′ 12 The noise figure of the three-stage cascade network of low noise amplifier, DUT and noise figure tester is F 123 , the gain is G 123 ; Step 1: Calibrate the noise figure meter; Step 2: Measure the noise figure F′ of the cascaded low-noise amplifier and the device under test 12 and gain G′ 12 ; Step 3: Measure the noise figure F1' and gain G1' of the low-noise amplifier; Step 4: Calculate the noise figure F2' and gain G'2 of the DUT; Step 1 specifically includes the following steps: Step 1.1: Connect the output of the noise source directly to the input of the noise figure meter. Step 1.2: Measure the noise figure F3 of the noise figure meter and store the hot and cold noise power of the noise source in the on and off states, recorded as N 3hot 、N 3cold ; Step 2 specifically includes the following steps: Step 2.1: Connect the noise source to the input port of the low-noise amplifier. Connect the output of the low-noise amplifier and the device under test in cascade connection to the input port of the noise figure meter. Step 2.2: Measure the noise figure F of the three-stage cascade network of the low noise amplifier, the device under test, and the noise figure tester 123 , and store the hot and cold noise power of the noise source in the on and off states, recorded as N 123hot 、N 123cold ; Step 2.3: The noise figure meter automatically calculates and displays the cascaded gain G′ of the low noise amplifier and the device under test. 12 and noise figure F′ 12 , the calculation formula is as follows: Step 3 specifically includes the following steps: Step 3.1: Connect the noise source to the input port of the low noise amplifier, and the output of the low noise amplifier to the input port of the noise figure meter; Step 3.2: Measure the noise figure of the cascaded low-noise amplifier and noise figure meter, denoted as F′ 13 , and store the hot and cold noise power of the noise source in the on and off states, recorded as N' 13hot , N′ 13cold ; Step 3.3: The noise figure meter automatically calculates and displays the gain G1' and noise figure F1' of the low noise amplifier. The calculation formula is as follows: Step 4 specifically includes the following steps: Step 4.1: The cascaded noise figure formula of the low noise amplifier and the device under test is: Step 4.2: Substitute the noise figure F′ measured in step 2.3 12 Substitute the gain G1' and noise figure F1' measured in step 3.3 into formula (9) to calculate the noise figure F2' of the device under test: F′2=(F′ 12 -F1')×G′1+1 (10); Step 4.3: Gain G′ measured according to step 2.3 12 The gain G′2 of the DUT is calculated based on the gain G′1 measured in step 3.3:

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