A test method for antenna harmonic spur transmission based on compact field

Abstract

The present application belongs to the field of electromagnetic compatibility test, and particularly relates to a kind of test method for completing antenna harmonic spurious radiation emission test using compact field, which can be used to replace traditional far field test method, and the method comprises the following steps: step 1) arranging compact field test system; step 2) configuring calibration path of test system; step 3) calculating the loss L of test system; step 4) comparing L with ideal loss L, when the difference between L and L meets the set value, entering step 5), otherwise, returning to step 3); step 5) configuring measurement path of test system; step 6) adjusting the direction of the antenna of EUT to be tested, to ensure that the test value is the maximum value; step 7) calculating the fundamental ERP of transmitter; step 8) measuring the value of harmonic and spurious radiation emission ERP, and comparing with the fundamental ERP, to judge whether the harmonic spurious radiation emission of the antenna of EUT to be tested meets the requirement of GJB151B, thereby completing the test. real ; step 4) comparing L with ideal loss L, when the difference between L and L meets the set value, entering step 5), otherwise, returning to step 3); step 5) configuring measurement path of test system; step 6) adjusting the direction of the antenna of EUT to be tested, to ensure that the test value is the maximum value; step 7) calculating the fundamental ERP of transmitter; step 8) measuring the value of harmonic and spurious radiation emission ERP, and comparing with the fundamental ERP, to judge whether the harmonic spurious radiation emission of the antenna of EUT to be tested meets the requirement of GJB151B, thereby completing the test. real ideal real ideal ​​​​

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic compatibility testing technology. Specifically, it relates to a test method that replaces the far-field test antenna harmonic distortion radiation emission test, and more particularly to a test method for antenna harmonic distortion radiation emission based on a compact field. Background Technology

[0002] Far-field testing is a commonly used method in antenna and electromagnetic compatibility (EMC) radiation testing. While this method has a long history, it suffers from various limitations. In far-field antenna and EMC testing, there are specific requirements for the test distance: the ratio of the square of the antenna's aperture to its wavelength must be the minimum required far-field distance. This limitation essentially means that in unrestricted free space, the diffraction of the wavefront results in a phase difference of less than 22.5°. For electrically large EUT antennas, this distance often reaches kilometers or even greater, making this testing method theoretically feasible but impractical in real-world testing. This problem frequently occurs in antenna and EMC testing. To address this issue in antenna testing, near-field and compacted-field testing methods have been proposed. Near-field testing methods have more complex algorithms and require higher scanning accuracy. Compact field testing, as an alternative to far-field testing, has garnered widespread attention since its inception. Compared to far-field methods, compact field testing significantly shortens the testing distance, and the distance required to reach far-field conditions is independent of wavelength and the aperture of the EUT antenna, depending only on the characteristics of the testing environment. This method has been widely applied and proven feasible in antenna testing. Its rationale lies in recognizing that the essence of the far field is the phase difference of the wavefront, not the distance. Therefore, as long as the phase difference requirement is met, it can be artificially adjusted to quickly achieve the far-field requirement over short distances. Among compact field testing methods, reflection-based, holographic, and phased array methods are the three most common forms. Considering the bandwidth and polarization requirements, the reflection-based compact field method is the most frequently used and has become the preferred method for testing electrically large antennas.

[0003] However, in the field of electromagnetic compatibility testing, there is still no research on this method of using a compressed field to replace the far field, even though it is theoretically entirely feasible. Summary of the Invention

[0004] To address the shortcomings of existing far-field electromagnetic compatibility (EMC) testing techniques due to excessive distance, this invention proposes a testing method for antenna harmonic distortion and radiated emission testing using a compressed field. This method meets the phase requirements stipulated for far-field conditions and can effectively replace existing far-field EMC testing methods. Furthermore, this method avoids the problem of continuously increasing far-field distance as the testing frequency of EMC testing increases.

[0005] This invention proposes a method for testing antenna harmonic distortion radiated emissions based on a compact field, the method comprising:

[0006] Step 1) Set up the compact field test system, including: a compact field consisting of a feed and a reflector, a vector network analyzer, a receiver, and a signal generator;

[0007] Step 2) Fix the antenna with known gain in the compact field quiet zone and configure the verification path of the test system;

[0008] Step 3) Calculate the empty loss L of the test system. real ;

[0009] Step 4) Place L real With ideal air loss L ideal For comparison, when L real With L ideal If the difference meets the set value, proceed to step 5); otherwise, return to step 3.

[0010] Step 5) Fix the EUT antenna under test in the compact field quiet zone and configure the measurement path of the test system;

[0011] Step 6) Adjust the pointing of the EUT antenna to ensure the test value is at its maximum value;

[0012] Step 7) Calculate the fundamental frequency ERP of the transmitter;

[0013] Step 8) Measure the values ​​of harmonic and spurious radiated emissions (ERP) and compare them with the fundamental ERP to determine whether the harmonic and spurious radiated emissions of the EUT antenna under test meet the requirements of GJB151B, thus completing the test.

[0014] As an improvement to the above technical solution, the receiver is an EMI receiver or a spectrum analyzer.

[0015] As an improvement to the above technical solution, step 2) specifically includes:

[0016] Connect the signal generator to the feed source, and use the feed source as the transmitting antenna; use the antenna with known gain as the receiving antenna, and connect it to the receiver.

[0017] As one improvement to the above technical solution, step 3) specifically includes:

[0018] The transmission coefficient S was measured using a vector network analyzer. 21 Let the gain of the feed antenna be G. f The gain of the quiet zone receiving antenna is G. r The absolute value of cable loss is L loss The formula for calculating the measured air loss is:

[0019] L real =S 21 -G t -G f +L loss .

[0020] As one improvement to the above technical solution, step 3) specifically includes:

[0021] Connect the feed antenna to a signal P with a known level. k The reading P at the frequency point to be measured is read using a receiver. r Let the gain of the feed antenna be G. f The gain of the quiet zone receiving antenna is G. r The absolute value of cable loss is L loss The formula for calculating the measured air loss is:

[0022] L real =P r -P k -G t -G f +L loss .

[0023] As an improvement to the above technical solution, in step 4), the difference satisfies the following formula:

[0024] |L real -L ideal | <3dB

[0025] in, R is the distance from the reflecting surface to the feed source, and λ is the wavelength.

[0026] As an improvement to the above technical solution, step 5) specifically includes:

[0027] Connect the signal generator to the antenna of the EUT under test, use the antenna of the EUT under test as the transmitting antenna, and use the feed source as the receiving antenna;

[0028] The antenna under test (EUT) is fixed to the compact field quiet zone with pins, and the geometric center of the EUT antenna coincides with the optimal position of the compact field quiet zone.

[0029] Connect the back end of the receiving antenna to the receiver; when the receiver exceeds its range, also connect the back end of the receiving antenna to the attenuator.

[0030] As one of the improvements to the above technical solution, step 6) specifically includes: keeping the EUT's placement position unchanged, adjusting the antenna's elevation and azimuth angles so that the maximum value of the EUT's radiation direction can be measured by the receiver.

[0031] As an improvement to the above technical solution, the calculation formula for step 7) is as follows:

[0032] ERP = P rec1 +L real +L loss -G f ;

[0033] In the formula, P rec1 To test the receiver readings during EUT testing, G f To measure the gain of the feed antenna, a frequency sweep test is performed across the entire test band until all required test frequencies are covered.

[0034] As one improvement to the above technical solution, step 8) specifically includes:

[0035] Record the values ​​of harmonic and spurious radiated emissions (ERPs) measured by frequency sweep. The absolute suppression of these harmonics should be less than -20 dBm. At the same time, compare these harmonic and spurious ERPs with the fundamental ERP to determine the relative value of the harmonic ERP. Compared with the fundamental, it should be 80 dB lower. Take the one with the looser suppression requirement. Determine whether the EUT under test meets the requirements according to the above standards. If it meets the requirements, it proves that the harmonic spurious radiated emissions test results meet the requirements. If it does not meet the requirements, it proves that the harmonic spurious radiated emissions test results do not meet the requirements of the standard.

[0036] The advantages of this invention compared to the prior art are:

[0037] The method proposed in this invention can solve the problems of insufficient test distance and increased test distance with increasing test frequency in the current far-field test method. It provides an alternative solution for situations where radiated emission testing could not be performed before, and solves the long-standing problem of electromagnetic compatibility harmonic distortion testing and evaluation. Attached Figure Description

[0038] Figure 1 This is a flowchart of the test method of the present invention for completing the antenna harmonic distortion radiation emission test using a compact field;

[0039] Figure 2 This is a system verification path configuration diagram;

[0040] Figure 3 This is a system measurement path configuration diagram. Detailed Implementation

[0041] This invention proposes a test method for antenna harmonic distortion radiation emission based on a compact field. The test method includes the following steps:

[0042] Step 1) Configure the system's verification path;

[0043] Step 2) Configure the verification path of the test system, verify the system's empty loss, use the feedhorn as the transmitting antenna, and use the antenna with known gain as the receiving antenna.

[0044] Step 3) Measure S using a vector network. 21 Let the gain of the feed antenna be G. f The gain of the quiet zone receiving antenna is G. r The cable loss is L loss (Absolute value), measured air loss L real =S 21 -G t -G f +L loss Alternatively, the feed antenna can be directly connected to a signal P with a known voltage level. k (dBW), the reading P at the frequency point to be measured is obtained using an EMI receiver or spectrum analyzer. r (dBW), cable loss is L loss (Absolute value), L real =P r (dBW)-P k (dBW)-G t -G f +L loss ;

[0045] Step 4) Place L real The formula for calculating air loss under ideal conditions L ideal Compare;

[0046] Step 5) Configure the measurement path of the test system;

[0047] Step 6) Adjust the pointing of the EUT antenna to ensure the test value is at its maximum value;

[0048] Step 7) Calculate the fundamental frequency ERP of the transmitter;

[0049] Step 8) Measure the values ​​of harmonic and spurious radiated emissions (ERP) and compare them with the fundamental ERP to determine whether the harmonic and spurious radiated emissions of the EUT antenna under test meet the requirements of GJB151B.

[0050] As one improvement to the above technical solution, step 1) specifically includes:

[0051] The test equipment required for setting up a compact field test site includes: a compact field system consisting of a feed and a reflector, a vector network analyzer, and a receiver (EMI receiver or spectrum analyzer).

[0052] As one improvement to the above technical solution, step 3) specifically includes:

[0053] The cable loss of the connecting cable was tested using a vector network analyzer and recorded as L. loss Using a vector network analyzer, the S-axis of the entire line from the feed antenna to the receiving antenna with known gain in the quiet zone is measured. 21 Alternatively, a receiver can be used to transmit a signal P with a known transmission level. k (dBW) Feed source, measuring the reading P at the receiver. r (dBW), then L real =S 21 -G t -G f +L loss Or L real =P r (dBW)-P k (dBW)-G t -G f +L loss ;

[0054] As an improvement to the above technical solution, step 4) specifically includes:

[0055] Calculate the measured air loss and compare it with the theoretical value. The theoretical air loss can be calculated using the formula... Calculation yields that if |L real -L ideal If | < 3dB, the verification process is complete, proceed to step 5). If it is greater than 3dB, the cause needs to be found and steps 1) to 4) need to be continued until it is less than 3dB.

[0056] As an improvement to the above technical solution, step 5) specifically includes:

[0057] The EUT under test is fixed to the compact field quiet zone with pins. The geometric center of the antenna coincides with the optimal position of the compact field quiet zone. The compact field feed antenna is used as the receiving antenna. The attenuator and receiver are connected to the rear end of the antenna.

[0058] As one improvement to the above technical solution, step 6) specifically includes:

[0059] With the EUT (Electronic Under Test) in a fixed position, the beam direction of the EUT is adjusted by moving the turntable.

[0060] As an improvement to the above technical solution, step 7) specifically includes:

[0061] The ERP calculation formula for the EUT under test can be expressed as follows:

[0062] ERP = P rec1 +L real +L loss -G f ;

[0063] In the formula P rec1 To test the receiver readings during EUT testing, a frequency sweep test is performed across the entire test band until all required test frequencies are covered. f This represents the antenna gain at each frequency point of the feed antenna.

[0064] As one improvement to the above technical solution, step 8) specifically includes:

[0065] Record the values ​​of harmonic and spurious radiated emissions (ERPs) measured by frequency sweep. The absolute suppression of these harmonics should be less than -20 dBm. At the same time, compare these harmonic and spurious ERPs with the fundamental ERP to determine the relative value of the harmonic ERP. Compared with the fundamental, it should be 80 dB lower. Take the one with the looser suppression requirement. Determine whether the EUT under test meets the requirements according to the above standards. If it meets the requirements, it proves that the harmonic spurious emission test results meet the requirements. If it does not meet the requirements, it proves that the harmonic spurious emission test results do not meet the requirements of the standard.

[0066] The technical solutions provided by the present invention will be further illustrated below with reference to the embodiments.

[0067] like Figure 1 The diagram shown is a flowchart of a test method for completing antenna harmonic distortion radiated emission testing using a compressed field, according to an embodiment of the present invention. The present invention provides a test method for completing antenna harmonic distortion radiated emission testing using a compressed field.

[0068] Step 1) Configure the system's verification path;

[0069] Specifically, step 1) includes:

[0070] The compact field test area needs to be set up, and the required test equipment includes: a compact field system consisting of a feed and a reflector, a vector network analyzer, and a receiver (EMI receiver or spectrum analyzer). The system calibration path should be configured as follows... Figure 2 As shown, the signal generator is connected to the transmitting antenna, the compact field feed is used as the receiving antenna, and an attenuator and receiver are configured. First, the possible range of receiver readings is estimated, and it is considered whether to add an attenuator to prevent receiver overload and possible damage to the test site.

[0071] Step 2) Configure the verification path of the test system, verify the system's empty loss, use the feedhorn as the transmitting antenna, and use the antenna with known gain as the receiving antenna.

[0072] Step 3) Test the cable loss of the connecting cable using a vector network analyzer and record it as L. loss Using a vector network analyzer, the S-axis of the entire line from the feed antenna to the receiving antenna with known gain in the quiet zone is measured. 21 Alternatively, a receiver can be used to transmit a signal P with a known transmission level. k (dBW) Feed source, measuring the reading P at the receiver. r (dBW), then L real =S 21 -G t -G f +L loss Or L real =P r (dBW)-P k (dBW)-G t -G f +L loss ;

[0073] Step 4) Place L real The formula for calculating air loss under ideal conditions L ideal Compare;

[0074] Specifically, step 4) includes:

[0075] Calculate the measured air loss and compare it with the theoretical value. The theoretical air loss can be calculated using the formula... Calculation yields that if |L real -L ideal If | < 3dB, the verification process is complete, proceed to step 5). If it is greater than 3dB, the cause needs to be found and steps 1) to 4) need to be continued until it is less than 3dB.

[0076] Step 5) Configure the measurement path;

[0077] Specifically, step 5) includes:

[0078] according to Figure 3 Configure the measurement path, use the EUT under test as the transmitter and the feed as the receiver, fix the EUT under test in the compact field quiet zone with pins, the geometric center of the antenna coincides with the optimal position of the compact field quiet zone, use the compact field feed antenna as the receiving antenna, and connect the attenuator and receiver to the rear end of the antenna.

[0079] Step 6) Adjust the pointer of the EUT under test to ensure that the test value is the maximum value;

[0080] Specifically, step 6) includes:

[0081] With the EUT's placement unchanged, adjust the elevation and azimuth angles so that the maximum value of the EUT's radiation direction can be measured by the receiver.

[0082] Step 7) Calculate the fundamental frequency ERP of the transmitter using the formula as a benchmark for comparing harmonic distortion radiation emissions;

[0083] Specifically, step 7) includes:

[0084] The formula for calculating the ERP (Effective Radiated Power) of the EUT under test can be expressed as follows:

[0085] ERP = P rec1 +L real +L loss -G f ;

[0086] In the formula P rec1 To test the receiver readings during EUT testing, a frequency sweep test is performed across the entire test band until all required test frequencies are covered. f The gain of the feed antenna at each frequency point.

[0087] Step 8) Measure the values ​​of harmonic and spurious radiated emission (ERP) and compare them with the fundamental ERP to determine whether the EUT under test meets the requirements of GJB151B.

[0088] Specifically, step 8) includes:

[0089] Record the values ​​of harmonic and spurious radiated emissions (ERPs) measured by frequency sweep. The absolute suppression of these harmonics should be less than -20 dBm. At the same time, compare these harmonic and spurious ERPs with the fundamental ERP to determine the relative value of the harmonic ERP. Compared with the fundamental, it should be 80 dB lower. Take the one with the looser suppression requirement. Determine whether the EUT under test meets the requirements according to the above standards. If it meets the requirements, it proves that the harmonic spurious emission test results meet the requirements. If it does not meet the requirements, it proves that the harmonic spurious emission test results do not meet the requirements of the standard.

[0090] As can be seen from the above detailed description of the present invention, the present invention realizes a test method that uses a compressed field to replace the harmonic distortion radiation emission of a far-field test antenna.

[0091] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of the present invention do not depart from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for testing harmonic and spurious emission of a compact range based antenna, the method comprising: Step 1) arranging a compact range test system, including: a compact range composed of a feed source and a reflector, a vector network analyzer, a receiver and a signal generator; Step 2) fixing an antenna with known gain in a quiet zone of the compact range, and configuring a calibration path of the test system; Step 3) Calculate the empty loss L of the test system real ; Step 4) L real is compared with the ideal air loss L ideal , when the difference between L real and L ideal satisfies a set value, Step 5) is entered, otherwise, Step 3) is returned. Step 5) fixing an EUT antenna to be tested in the quiet zone of the compact range, and configuring a measurement path of the test system; Step 6) adjusting a pointing direction of the EUT antenna to be tested, so as to ensure that a test value is a maximum value; Step 7) calculating a fundamental ERP of the transmitter; Step 8) measuring values of harmonic and spurious emission ERPs, and comparing the values with the fundamental ERP, so as to determine whether the harmonic and spurious emission of the EUT antenna to be tested meets requirements of GJB151B, thereby completing the test. The step 3) specifically comprises: Transmission coefficient S is measured by vector network analyzer 21 , set the gain of the feed antenna G f , the gain of the quiet zone receiving antenna G r , the absolute value of cable loss L loss , the calculation formula of the measured air loss is: L real＝ S 21 -G t -G f +L loss The step 3) specifically comprises: The feed antenna is connected to a signal P of known level k The receiver reads the indication P of the frequency point to be measured r The gain of the feed antenna is G f The gain of the quiet zone receiving antenna is G r The absolute value of the cable loss is L loss The formula for calculating the actual loss is L real＝ P r -P k -G t -G f +L loss .

2. The compacted field based antenna spurious emissions test method of claim 1, wherein, The receiver is an EMI receiver or a spectrum analyzer.

3. The compact field based antenna spurious emissions test method of claim 1, wherein, The step 2) specifically comprises: The signal generator is connected to the feed source, the feed source is used as a transmitting antenna, and the antenna with known gain is used as a receiving antenna and connected to the receiver.

4. The compact field based antenna spurious emissions test method of claim 1, wherein, In the step 4), the difference satisfies the following formula: |L real -L ideal |<3dB wherein R is the distance from the reflector to the feed, and λ is the wavelength.

5. The compact field based antenna spurious emissions test method of claim 1, wherein, The step 5) specifically comprises: The signal generator is connected to the EUT antenna to be tested, the EUT antenna to be tested is used as a transmitting antenna, and the feed source is used as a receiving antenna; The EUT antenna to be tested is fixed to the quiet zone of the compact range by a pin, and a geometric center of the EUT antenna to be tested coincides with an optimal position of the quiet zone of the compact range; The back end of the receiving antenna is connected to the receiver, and when the receiver exceeds a range, the back end of the receiving antenna is also connected to an attenuator.

6. The compact field based antenna spurious emissions test method of claim 1, wherein, The step 6) specifically comprises: keeping a placement position of the EUT unchanged, adjusting an elevation angle and an azimuth angle of the antenna, so that a maximum value of a radiation direction of the EUT can be measured by the receiver.

7. The compact field based antenna spurious emissions test method of claim 1, wherein, The calculation formula of the step 7) is: ERP = P rec1 +L real +L loss -G f ; In the formula, P rec1 To test the receiver readings during EUT testing, G f To measure the gain of the feed antenna, a frequency sweep test is performed across the entire test band until all required test frequencies are covered.

8. The compact field based antenna spurious emissions class test method of claim 1, wherein, The step 8) specifically comprises: According to a set judgment standard, it is determined whether the EUT to be tested meets requirements, if the requirements are met, it is proved that the test result of the harmonic and spurious emission meets the requirements, if the requirements are not met, it is proved that the test result of the harmonic and spurious emission does not meet the standard requirements; The set judgment standard is that: values of the harmonic and spurious emission ERPs measured by the frequency sweeping are recorded, absolute values of the harmonics are required to be suppressed by less than -20 dBm, and the harmonic and spurious ERPs are compared with the fundamental ERP, it is determined that a relative value of the harmonic ERP is 80 dB lower than the fundamental ERP, and a requirement of a lower suppression is taken in the two.

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