A GNSS navigation signal coexistence test system and a sensitivity threshold evaluation method

Abstract

This invention discloses a GNSS navigation signal coexistence test system and a sensitivity threshold evaluation method, relating to the field of electromagnetic compatibility testing technology. The system includes a reverberation chamber, a GNSS navigation signal transponder, a GNSS navigation signal receiver, and a host computer. The reverberation chamber includes a mechanical stirrer, a radio frequency signal source, a radio frequency power amplifier, a spectrum analyzer, a transmitting antenna T, and a receiving antenna R. The GNSS navigation signal transponder includes a transponder terminal, a transponder receiving antenna TR, and a transponder transmitting antenna TT. The GNSS navigation signal receiver includes a receiving terminal and a receiving antenna RR. Utilizing the multipath scattering characteristics of the reverberation chamber, the system simulates the fading characteristics of wireless signals in a real environment. Furthermore, leveraging the high quality factor of the reverberation chamber, a high-level test environment is created over a wide frequency range with relatively low input power, enabling GNSS navigation signal coexistence testing and quantitative evaluation and analysis of sensitivity thresholds.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic compatibility testing technology, and in particular to a GNSS navigation signal coexistence testing system and a sensitivity threshold evaluation method. Background Technology

[0002] Global Navigation Satellite System (GNSS) is widely used in low-altitude economic fields such as general aviation manned flight, unmanned logistics, unmanned inspection, unmanned exploration, unmanned surveying and mapping, and unmanned remote sensing.

[0003] However, with the widespread application of high-power frequency-consuming electronic devices or systems such as wireless communication base stations, portable mobile terminals, new phased array radars, high-speed frequency-hopping radios, and electronic countermeasure jammers, the problem of anti-interference coexistence of multiple wireless signals has become prominent, leading to a series of wireless communication quality problems such as large transmission delays and high bit error rates.

[0004] In existing technologies, GNSS navigation signal coexistence testing and sensitivity threshold assessment are mainly conducted in plane wave test environments such as anechoic chambers or simulated open fields. First, the testing and evaluation process needs to simulate the multipath effect of wireless signals in real environments, and the simulation results in anechoic chambers or simulated open fields deviate significantly from the statistical characteristics of actual environments. Second, due to limitations of test instruments such as antennas and power amplifiers, the test levels that can be generated in anechoic chambers or simulated open fields are limited, making it difficult to assess the coexistence performance, anti-interference margin, and sensitivity threshold of GNSS navigation signals. Finally, existing standards mainly test narrowband signals and cannot reflect the coexistence capability of GNSS navigation signals in the 100MHz-18GHz broadband range.

[0005] Therefore, a GNSS navigation signal coexistence test system and a sensitivity threshold evaluation method are provided to solve the above problems. Summary of the Invention

[0006] The purpose of this invention is to provide a GNSS navigation signal coexistence test system and a sensitivity threshold evaluation method, which simulates the fading characteristics of wireless signals in a real environment, improves the evaluation accuracy of the anti-interference coexistence capability of GNSS navigation signals under multipath effects, forms a high-level test environment in a wide frequency band, and provides theoretical and experimental support for evaluating the sensitivity thresholds affecting the coexistence of GNSS navigation signals.

[0007] To achieve the above objectives, the present invention provides a GNSS navigation signal coexistence test system, comprising a reverberation chamber, a GNSS navigation signal transponder, a GNSS navigation signal receiver, and a host computer. The reverberation chamber includes a mechanical stirrer, a radio frequency signal source, a radio frequency power amplifier, a spectrum analyzer, a transmitting antenna T, and a receiving antenna R. The GNSS navigation signal transponder includes a transponder terminal, a transponder receiving antenna TR, and a transponder transmitting antenna TT. The GNSS navigation signal receiver includes a receiving terminal and a receiving antenna RR.

[0008] Preferably, the RF signal source and the RF power amplifier are connected by an RF coaxial cable, the RF power amplifier and the transmitting antenna T are connected by a cable, the spectrum analyzer and the receiving antenna R are connected by a cable, the repeater terminal and the repeater receiving antenna TR are connected by a cable, the repeater terminal and the repeater transmitting antenna TT are connected by a cable, the host computer and the receiving terminal are connected by a cable, and the receiving terminal and the receiving antenna RR are connected by a cable.

[0009] Preferably, the relay terminal, the relay receiving antenna TR, and the host computer are all located outside the reverberation chamber. The host computer is a computer PC, which has a monitoring unit inside. The relay transmitting antenna TT, the receiving terminal, and the receiving antenna RR are all located inside the reverberation chamber. The distance between the receiving terminal and the metal wall, and the distance between the receiving antenna RR and the metal wall, are not less than one-quarter of the wavelength of the test frequency.

[0010] A sensitivity threshold evaluation method for a GNSS navigation signal coexistence test system includes the following steps:

[0011] S1: Configure the internal experimental environment of the reverberation chamber to determine the test frequency range of the GNSS navigation signal receiver under test. Frequency interval and test level E p Position the mechanical mixer j Set as j =0;

[0012] S2: The mechanical stirrer steps to position. j = j +1, for a given frequency Injected input power To form a test level E p ;

[0013] S3: For a given frequency Based on the three-dimensional coordinates, determine the desired test level. E p The coexistence capability of GNSS navigation signals is recorded. If GNSS navigation signals coexist, the input power is recorded. Corresponding peak field strength and peak received power ;

[0014] S4: If there is a coexistence problem with GNSS navigation signals, adjust the input power. This allows GNSS navigation signals to coexist, and records and inputs power. Corresponding peak field strength and peak received power ;

[0015] S5: Determine the location of the mechanical stirrer j With the set number of positions N The relationship between the positions of the mechanical stirrer and the position of the mechanical stirrer j Not greater than the set number of positions N Repeat steps S1 to S4;

[0016] S6: If the mechanical stirrer is in position j Greater than the set number of positions N， For any frequency Record separately N Test level corresponding to the coexistence of multiple GNSS navigation signals E p Extract test level E p The minimum value is used as the frequency. The sensitivity threshold for the coexistence of GNSS navigation signals.

[0017] Preferably, in step S1, the test level E p Set to the maximum field strength expected for the coexistence of GNSS navigation signals in a real-world environment.

[0018] Preferably, in step S1, configuring the internal experimental environment of the reverberation chamber specifically includes the following steps:

[0019] S11: Set the forwarding transmitting antenna TT inside the reverberation chamber, set the forwarding terminal and forwarding receiving antenna TR outside the reverberation chamber, set the receiving terminal and receiving antenna RR inside the working space of the reverberation chamber, and connect the receiving terminal and the host computer.

[0020] S12: No electromagnetic interference signals are applied in the reverberation chamber. Debug the GNSS navigation transponder and GNSS navigation receiver, and set the three-dimensional coordinates as the reference index.

[0021] S13: Point the transmitting antenna T to the corner of the reverberation chamber and set the receiving antenna R inside the working space of the reverberation chamber.

[0022] Preferably, step S2 specifically includes the following steps:

[0023] S21: From the starting frequency Begin by adjusting the radio frequency signal source and injecting input power into the transmitting antenna T. A test level is established in the reverberation chamber. E p ;

[0024] S22: Monitor the received power within the reverberation chamber using the receiving antenna R and a spectrum analyzer. .

[0025] Preferably, in step S21, the input power Specifically set as follows:

[0026] ;

[0027] in, AVF This represents the ratio of the average received power to the input power in the no-load state of the reverberation chamber. CVF This represents the ratio of average received power to input power under reverberation chamber loading conditions. E test Indicates field strength. This represents the normalized mean field strength under no-load conditions in the reverberation chamber.

[0028] Therefore, the present invention employs the above-mentioned GNSS navigation signal coexistence test system and sensitivity threshold evaluation method, which has the following beneficial effects:

[0029] (1) This scheme simulates the electromagnetic fading characteristics of wireless signals in a real environment by using an electromagnetic reverberation chamber. By changing the field distribution inside the chamber with a mechanical stirrer or an electronic stirrer, the same fading conditions can be accurately reproduced, which is convenient for repeated testing and result comparison.

[0030] (2) This scheme utilizes the high quality factor of the reverberation chamber to form a high-level test environment with a small input power in a wide frequency range, while ensuring the accuracy, repeatability and statistical reliability of the test. It can accurately find the critical field strength of equipment failure and improve the accuracy of threshold assessment.

[0031] (3) This solution does not require the construction of a complex environment on-site, which can significantly reduce testing costs and time. By rapidly stirring, a large number of decay samples are generated, and long-term statistical characteristics can be evaluated in a short time.

[0032] The method of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0033] Figure 1This is a structural diagram of a GNSS navigation signal coexistence test system according to the present invention;

[0034] Figure 2 This is a flowchart of a sensitivity threshold evaluation method for a GNSS navigation signal coexistence test system according to the present invention;

[0035] Figure 3 This is a schematic diagram of the signal control principle of a GNSS navigation signal coexistence test system according to the present invention.

[0036] The components are: 1. Host computer; 2. Mechanical stirrer; 3. Radio frequency signal source; 4. Radio frequency power amplifier; 5. Spectrum analyzer; 6. Transmitting antenna T; 7. Receiving antenna R; 8. Relay terminal; 9. Relay receiving antenna TR; 10. Relay transmitting antenna TT; 11. Receiving terminal; 12. Receiving antenna RR. Detailed Implementation

[0037] The method of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0038] Unless otherwise defined, the methodological or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0039] The terms "comprising" or "including" as used in this invention mean that the element preceding the term encompasses the element listed after the term, and do not exclude the possibility of encompassing other elements. Terms such as "inner," "outer," "upper," and "lower" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. When the absolute position of the described object changes, the relative positional relationship may also change accordingly. In this invention, unless otherwise explicitly specified and limited, the term "attached" and similar terms should be interpreted broadly. For example, it can refer to a fixed connection, a detachable connection, or an integral part; it can refer to a direct connection or an indirect connection through an intermediate medium; it can refer to the internal communication of two elements or the interaction relationship between two elements. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0040] Example

[0041] like Figure 1As shown, this embodiment provides a GNSS navigation signal coexistence test system, including a reverberation chamber, a GNSS navigation signal transponder, a GNSS navigation signal receiver, and a host computer 1. The reverberation chamber includes a mechanical stirrer 2, a radio frequency signal source 3, a radio frequency power amplifier 4, a spectrum analyzer 5, a transmitting antenna T6, and a receiving antenna R7, forming the required peak field strength in a wide frequency range of 100MHz-18GHz. It also simulates the multipath scattering of electromagnetic waves in a real environment through reflection from the wall.

[0042] The GNSS navigation signal transponder includes a transponder terminal 8, a transponder receiving antenna TR9, and a transponder transmitting antenna TT10. The GNSS navigation signal receiver includes a receiving terminal 11 and a receiving antenna RR12.

[0043] For the reverberation chamber, the mechanical stirrer 2 is controlled by the host computer 1 to step, thereby changing the boundary conditions inside the chamber. Finally, a statistically uniform and randomly polarized test environment is formed in the working space at a distance of not less than one-quarter wavelength of the lowest usable frequency from the chamber wall.

[0044] Due to the high quality factor of the reverberation chamber, a relatively small input power is injected through the transmitting antenna T6. It can generate a large field strength. E test Regarding this characteristic, at a given frequency The host computer 1 controls the output and frequency of the radio frequency signal source 3. The corresponding signal level, after being amplified by RF power amplifier 4, is injected into the reverberation chamber by transmitting antenna T6, forming the test level required for GNSS navigation signal coexistence testing within the reverberation chamber. E p .

[0045] Meanwhile, in order to ensure that a certain amount of power is injected into the reverberation chamber, it is also necessary to measure the received power using the receiving antenna R7 placed in the workspace. The power level is displayed by the spectrum analyzer 5, and the received power is recorded and saved by the host computer 1. .

[0046] For GNSS navigation, the receiving antenna TR9 receives the GNSS navigation signal and inputs it to the receiving terminal 11. Then, it is transmitted to the reverberation chamber via the transmitting antenna TT10. In the reverberation chamber, the navigation signal is transmitted multiple times through the metal wall, which can be used to simulate the multipath reflection effect in a real environment. Based on this characteristic, the receiving antenna RR12 receives the GNSS navigation signal and forwards it to the host computer 1 via the receiving terminal 11. The coexistence capability of the GNSS navigation signal is determined by the three-dimensional coordinates of the navigation signal.

[0047] The radio frequency signal source 3 and the radio frequency power amplifier 4 are connected by a radio frequency coaxial cable. The radio frequency power amplifier 4 and the transmitting antenna T6 are connected by a cable. The spectrum analyzer 5 and the receiving antenna R7 are connected by a cable. The repeater terminal 8 and the repeater receiving antenna TR9 are connected by a cable. The repeater terminal 8 and the repeater transmitting antenna TT10 are connected by a cable. The host computer 1 and the receiving terminal 11 are connected by a cable. The receiving terminal 11 and the receiving antenna RR12 are connected by a cable.

[0048] The relay terminal 8, the relay receiving antenna TR9, and the host computer 1 are all located outside the reverberation chamber. The host computer 1 is a computer PC, which has a monitoring unit inside to control the reverberation chamber system and monitor GNSS navigation signals under electromagnetic interference.

[0049] The transmitting antenna TT10, receiving terminal 11, and receiving antenna RR12 are all located inside the reverberation chamber. The distance between receiving terminal 11 and the metal wall, and the distance between receiving antenna RR12 and the metal wall, are all no less than one-quarter wavelength of the test frequency.

[0050] like Figure 2 As shown, a sensitivity threshold evaluation method for a GNSS navigation signal coexistence test system includes the following steps:

[0051] S1: Configure the internal experimental environment of the reverberation chamber to determine the test frequency range of the GNSS navigation signal receiver under test. Frequency interval and test level E p Position the mechanical mixer j Set as j =0;

[0052] In step S1, the test level E p Set to the maximum field strength expected for the coexistence of GNSS navigation signals in a real-world environment.

[0053] In step S1, the internal experimental environment of the reverberation chamber is configured, specifically including the following steps:

[0054] S11: Set the forwarding transmitting antenna TT inside the reverberation chamber, set the forwarding terminal and forwarding receiving antenna TR outside the reverberation chamber, set the receiving terminal and receiving antenna RR inside the working space of the reverberation chamber, and connect the receiving terminal and the host computer.

[0055] S12: No electromagnetic interference signals are applied in the reverberation chamber. Debug the GNSS navigation transponder and GNSS navigation receiver, set the three-dimensional coordinates as reference indicators, and ensure that the GNSS navigation receiver works normally.

[0056] S13: Point the transmitting antenna T towards the corner of the reverberation chamber to avoid direct illumination of the antenna and GNSS navigation receiver terminal in the workspace, and set the receiving antenna R inside the workspace of the reverberation chamber.

[0057] S2: The mechanical stirrer steps to position. j = j +1, for a given frequency Injected input power To form a test level E p ;

[0058] Step S2 specifically includes the following steps:

[0059] S21: From the starting frequency Begin by adjusting the radio frequency signal source and injecting input power into the transmitting antenna T. A test level is established in the reverberation chamber. E p ;

[0060] In step S21, the input power Specifically set as follows:

[0061]

[0062] in, AVF This represents the ratio of the average received power to the input power in the no-load state of the reverberation chamber. CVF This represents the ratio of average received power to input power under reverberation chamber loading conditions. E test Indicates field strength. This represents the normalized mean field strength under no-load conditions in the reverberation chamber.

[0063] S22: Monitor the received power within the reverberation chamber using the receiving antenna R and a spectrum analyzer. .

[0064] S3: For a given frequency Based on the three-dimensional coordinates, determine the desired test level. E p The coexistence capability of GNSS navigation signals is then tested. If GNSS navigation signals coexist, it indicates that the GNSS navigation receiver under test is working properly. The input power is then recorded. Corresponding peak field strength and peak received power ;

[0065] S4: If there is a coexistence problem with GNSS navigation signals, it indicates that the GNSS navigation receiver under test is being interfered with and is malfunctioning. Adjust the input power. Input power Reduce the test level in the reverberation chamber. E p This also reduces the power accordingly, allowing GNSS navigation signals to coexist, and recording and input power. Corresponding peak field strength and peak received power ;

[0066] S5: The mechanical stirrer is controlled by a host computer to move in a stepping motion. N This location determines the position of the mechanical mixer. j With the set number of positions N The relationship between the positions of the mechanical stirrer and the position of the mechanical stirrer j Not greater than the set number of positions N Repeat steps S1 to S4;

[0067] S6: If the mechanical stirrer is in position j Greater than the set number of positions N， For any frequency Record separately N Test level corresponding to the coexistence of multiple GNSS navigation signals E p Extract test level E p The minimum value is used as the frequency. The sensitivity threshold for the coexistence of GNSS navigation signals.

[0068] For a given frequency and N At each position, at the test level E p If GNSS navigation signals can coexist under the influence of the test level, it indicates that the GNSS navigation receiver under test is working normally. E p The threshold for GNSS navigation signal coexistence sensitivity; if at the test level E p The GNSS navigation receiver under test malfunctioned under the influence of reduced input power. Post-test level E p Reduced to peak field strength And in N If the GNSS navigation receiver under test can function normally at all locations, it indicates that the peak field strength is... The threshold for sensitivity to the coexistence of GNSS navigation signals.

[0069] like Figure 3 As shown, the host computer 1 sets the given frequency of the radio frequency signal source 3 online. and level 1. Set the initial position of the mechanical mixer 2 j 1. Select typical indicators of GNSS navigation signals. In this embodiment, the typical indicator selected is three-dimensional coordinates.

[0070] Before starting the test, no electromagnetic interference was applied to ensure stable GNSS navigation communication was established within the reverberation chamber. After the test began, the virtual switch was turned on, and the signal was transmitted at a given frequency. The level of radio frequency signal source 3 With the gain of RF power amplifier 4 G Added together, this serves as the injected input power for the reverberation chamber. And to form the desired test level. E p ;

[0071] Based on virtual diagnostics, at the test level E p Determine whether the selected typical indicators are normal under the influence of the test. If they are normal, proceed according to the test frequency range. Select the test frequency points sequentially, and then control the injected input power again via a virtual switch. And use virtual diagnosis to determine whether typical indicators are normal;

[0072] If the selected typical indicators are determined to be abnormal based on virtual diagnostics, then the indoor test level for electromagnetic reverberation needs to be reduced. E p That is, adjusting the signal level of radio frequency signal source 3. set up;

[0073] For mechanical mixer 2, set the number of mixing positions. N Based on the virtual judgment, determine ceil( k / n )and N The relative size, where ceil is the floor function. k =count, indicating that the virtual switch is in the off state and the signal level of RF signal source 3 is... The count, where count is the counting function. n For the test frequency range The corresponding frequency number;

[0074] In particular, when k =1, n =20, ceil( k / n )=1; k =15, n =20, ceil(k / n )=1; k =21, n =20, ceil( k / n )=2;

[0075] If ceil( k / n )≤ N Then, according to virtual logic operations, using j = j +ceil( k / n Calculate the current position; otherwise, end the test.

[0076] Therefore, the present invention adopts the above-mentioned GNSS navigation signal coexistence test system and sensitivity threshold evaluation method, which utilizes the multipath scattering characteristics of the reverberation chamber to simulate the fading characteristics of wireless signals in the real environment, and utilizes the high quality factor of the reverberation chamber to form a high-level test environment with a small input power in a wide frequency range, thereby realizing GNSS navigation signal coexistence test and quantitative evaluation and analysis of sensitivity threshold.

[0077] Finally, it should be noted that the above embodiments are only used to illustrate the method of the present invention and not to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the method of the present invention, and these modifications or equivalent substitutions should not cause the modified method to deviate from the spirit and scope of the method of the present invention.

Claims

1. A GNSS navigation signal coexistence test system, characterized in that, It includes a reverberation chamber, a GNSS navigation signal transponder, a GNSS navigation signal receiver, and a host computer. The reverberation chamber includes a mechanical stirrer, a radio frequency signal source, a radio frequency power amplifier, a spectrum analyzer, a transmitting antenna T, and a receiving antenna R. The GNSS navigation signal transponder includes a transponder terminal, a transponder receiving antenna TR, and a transponder transmitting antenna TT. The GNSS navigation signal receiver includes a receiving terminal and a receiving antenna RR. The radio frequency signal source and the radio frequency power amplifier are connected by a radio frequency coaxial cable. The radio frequency power amplifier and the transmitting antenna T are connected by a cable. The spectrum analyzer and the receiving antenna R are connected by a cable. The repeater terminal and the repeater receiving antenna TR are connected by a cable. The repeater terminal and the repeater transmitting antenna TT are connected by a cable. The host computer and the receiving terminal are connected by a cable. The receiving terminal and the receiving antenna RR are connected by a cable. The relay terminal, the relay receiving antenna TR, and the host computer are all located outside the reverberation chamber. The host computer is a PC, which has a monitoring unit inside. The relay transmitting antenna TT, the receiving terminal, and the receiving antenna RR are all located inside the reverberation chamber. The distance between the receiving terminal and the metal wall, and the distance between the receiving antenna RR and the metal wall, are not less than one-quarter wavelength of the test frequency.

2. A sensitivity threshold evaluation method for a GNSS navigation signal coexistence test system as described in claim 1, characterized in that, Includes the following steps: S1: Configure the internal experimental environment of the reverberation chamber to determine the test frequency range of the GNSS navigation signal receiver under test. 、 Frequency interval and test level Position the mechanical mixer Set as ; S2: The mechanical stirrer steps to position. For a given frequency Injected input power To form a test level ; S3: For a given frequency Based on the three-dimensional coordinates, determine the desired test level. The coexistence capability of GNSS navigation signals is recorded. If GNSS navigation signals coexist, the input power is recorded. Corresponding peak field strength and peak received power ; S4: If there is a coexistence problem with GNSS navigation signals, adjust the input power. This allows GNSS navigation signals to coexist, and records and inputs power. Corresponding peak field strength and peak received power ; S5: Determine the location of the mechanical stirrer With the set number of positions The relationship between the positions of the mechanical stirrer and the mechanical stirrer No more than the set number of positions Repeat steps S1 to S4; S6: If the mechanical stirrer is in position Greater than the set number of positions ， For any frequency Record separately Test level corresponding to the coexistence of multiple GNSS navigation signals Extract test level The minimum value is used as the frequency. The sensitivity threshold for the coexistence of GNSS navigation signals.

3. The sensitivity threshold evaluation method for a GNSS navigation signal coexistence test system according to claim 2, characterized in that, In step S1, the test level Set to the maximum field strength expected for the coexistence of GNSS navigation signals in a real-world environment.

4. The sensitivity threshold evaluation method for a GNSS navigation signal coexistence test system according to claim 2, characterized in that, In step S1, the internal experimental environment of the reverberation chamber is configured, specifically including the following steps: S11: Set the forwarding transmitting antenna TT inside the reverberation chamber, set the forwarding terminal and forwarding receiving antenna TR outside the reverberation chamber, set the receiving terminal and receiving antenna RR inside the working space of the reverberation chamber, and connect the receiving terminal and the host computer. S12: No electromagnetic interference signals are applied in the reverberation chamber. Debug the GNSS navigation transponder and GNSS navigation receiver, and set the three-dimensional coordinates as the reference index. S13: Point the transmitting antenna T to the corner of the reverberation chamber and set the receiving antenna R inside the working space of the reverberation chamber.

5. The sensitivity threshold evaluation method for a GNSS navigation signal coexistence test system according to claim 2, characterized in that, Step S2 specifically includes the following steps: S21: From the starting frequency Begin by adjusting the radio frequency signal source and injecting input power into the transmitting antenna T. A test level is established in the reverberation chamber. ; S22: Monitor the received power within the reverberation chamber using the receiving antenna R and a spectrum analyzer. .

6. The sensitivity threshold evaluation method for a GNSS navigation signal coexistence test system according to claim 5, characterized in that, In step S21, the input power Specifically set as follows: ； in, AVF This represents the ratio of the average received power to the input power in the no-load state of the reverberation chamber. CVF This represents the ratio of average received power to input power under reverberation chamber loading conditions. Indicates field strength. This represents the normalized mean field strength under no-load conditions in the reverberation chamber.

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