A method for measuring ultra-high shielding effectiveness

Abstract

The application relates to a kind of ultra-high shielding effectiveness measurement methods, comprising: step S1, shielding effectiveness measurement system is built;Step S2, the frequency deviation of signal source transmitting signal frequency and signal analyzer corresponding received signal frequency is measured, and the frequency of all test frequency points corresponding to the frequency set when shielding effectiveness measurement is carried out is compensated;Step S3, after completing frequency offset compensation, 1dB compression point test is carried out to signal analyzer, the 1dB compression point power of signal analyzer under all test frequency points is acquired, and the dynamic matching power of signal source under all test frequency points is calculated;Step S4, reference level measurement system is built, and the reference level of signal analyzer under all test frequency points is measured;Step S5, the power value corresponding to all test frequency points after shielding is measured in shielding effectiveness measurement system, and the shielding effectiveness of the shielding room to be measured is acquired according to the reference level.The application realizes the requirement of ultra-high performance shielding effectiveness measurement.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of radio astronomy, and more particularly to a method for measuring super-high shielding effectiveness. BACKGROUND

[0002] Large radio telescopes have very high system sensitivity, for example, the system noise temperature of the current L, S and C bands is only a few tens of K. Large radio telescopes involve a large number of non-standard instruments and equipment, and the very high system sensitivity and continuous coverage of the observation bandwidth make radio astronomy observation very susceptible to external electromagnetic environment and system itself device electromagnetic radiation interference, and electromagnetic compatibility problem is prominent.

[0003] While radio astronomers are solving the problem of super-high performance electromagnetic shielding scheme of radio telescopes, the technical challenge that comes with it is how to verify whether the performance meets the requirements through shielding effectiveness measurement, and explore the capability limit of shielding effectiveness measurement. The existing shielding effectiveness measurement method is based on the standard, such as GB / T12190-2021, but the standard only gives the basic measurement requirements, and cannot meet the requirements of super-high shielding effectiveness measurement, such as shielding effectiveness measurement of more than 120dB. SUMMARY

[0004] To solve the above problems in the prior art, the present application provides a method for measuring super-high shielding effectiveness to meet the requirements of super-high performance shielding effectiveness measurement.

[0005] The present application provides a method for measuring super-high shielding effectiveness, comprising:

[0006] Step S1, a shielding effectiveness measurement system is built, the shielding effectiveness measurement system comprises a transmitting device, a receiving device and a control device connected with the transmitting device and the receiving device; the transmitting device comprises a signal source, a transmitting antenna connected with the signal source and a first photoelectric converter connected with the signal source, the transmitting antenna is installed in a shielding chamber to be measured; the receiving device comprises a signal analyzer and a receiving antenna connected with the signal analyzer, an amplifier is arranged at the front end of the receiving antenna; the control device comprises a control system and a second photoelectric converter connected with the control system, the second photoelectric converter is connected with the first photoelectric converter and connected with the signal analyzer;

[0007] Step S2, the signal source and the signal analyzer are taken out, the frequency deviation of the signal source transmitting signal frequency and the corresponding receiving signal frequency of the signal analyzer is measured, the frequency deviation of the frequency corresponding to all test frequency points set when shielding effectiveness measurement is performed is compensated, and the frequency after frequency deviation compensation is obtained;

[0008] Step S3, after the frequency offset compensation is completed, the 1dB compression point test is performed on the signal analyzer, the 1dB compression point power of the signal analyzer at all the test frequencies is obtained, and the dynamic matching power of the signal source at all the test frequencies is calculated;

[0009] Step S4, the signal source and the signal analyzer are returned to the shielding effectiveness measurement system, the shielding chamber to be measured is left, the transmitting device and the receiving device are placed in the microwave darkroom, the reference level measurement system is built, and the reference level of the signal analyzer at all the test frequencies is measured.

[0010] Step S5, the microwave darkroom is left, the shielding chamber to be measured is returned, the power values corresponding to all the test frequencies after shielding are measured, and the shielding effectiveness of the shielding chamber to be measured is obtained according to the reference level.

[0011] Further, the step S2 comprises:

[0012] Step S21, the signal source and the signal analyzer taken out are directly connected through the radio frequency cable, and the frequency offset measurement system is built;

[0013] Step S22, the initial center frequency of the signal analyzer and the frequency of the signal source transmitting signal are both set as the frequency f1(m) corresponding to the frequency offset measurement frequency point, and the sweep bandwidth of the signal analyzer is set, and the actual receiving frequency of the signal analyzer at each frequency offset measurement frequency point is recorded; wherein m = 1, 2, …, M, and M represents the number of frequency points set when the frequency offset is measured;

[0014] Step S23, the frequency offset value f3(m) = f2(m)-f1(m) of each frequency offset measurement frequency point is calculated, and f2(m) is the actual receiving frequency of the signal analyzer corresponding to the frequency point f1(m);

[0015] Step S24, the M frequency offset values f3(m) obtained are fitted to obtain a frequency offset curve function;

[0016] Step S25, according to the frequency offset curve function, the frequency offset compensation is performed on the frequencies corresponding to all the test frequencies set when the shielding effectiveness is measured, and the frequency F(n) after the frequency offset compensation is obtained, n = 1, 2, …, N, and N represents the number of test frequencies set when the shielding effectiveness is measured. SA

[0017] Further, the step S3 of obtaining the 1dB compression point power of the signal analyzer at all the test frequencies comprises:

[0018] ​Step S311: Initialize n=1, set the step value of the signal source transmission power to ΔP, and reset the sweep bandwidth, the number of scan points within the sweep bandwidth, the resolution bandwidth, and the video filter bandwidth of the signal analyzer.

[0019] Step S312, for the nth test frequency point, the initial transmit power of its signal source is denoted as P. in,0 (n), where the initial received power of the signal analyzer is denoted as P. out,0 (n), the signal source transmission power is gradually increased according to the step value ΔP, and the formula (P) is obtained during the process of gradually increasing the signal source transmission power. in,k (n)-P in,0 (n))-(P out,k (n)-P out,0 (n))=1dB+L c The signal source transmission power P corresponding to time (n) in,k (n), thereby obtaining the 1dB compression point power P of the signal analyzer at this frequency. out,k (n); where k represents the number of steps in the signal source's transmit power at the nth test frequency, and P in,k (n) represents the output power of the signal source when it reaches the 1dB compression point of the signal analyzer at the nth test frequency; L c (n) represents the cable loss value corresponding to the nth test frequency point; n = 1, 2, ..., N, where N represents the number of test frequencies set when measuring shielding effectiveness;

[0020] Step S313: Let n = n + 1, return to step S312, and continue until n = N. Obtain the 1dB compression point power of the signal analyzer at all test frequencies. The 1dB compression point power corresponding to the nth test frequency is denoted as P. out (n).

[0021] Further, the calculation of the dynamic matching power of the signal source at all test frequency points in step S3 includes:

[0022] Step S321, adjust the frequency F after frequency offset compensation. SA (n) is set as the center frequency of the signal analyzer and the antenna frequency. The signal source transmission frequency f0(n) is set as the amplifier frequency and the RF cable frequency. The input port power P corresponding to the amplifier frequency f0(n) is calculated. a,in (n) and output port power P a,out (n);

[0023] Step S322, based on the input port power P a,in (n) and the output port power P a,out (n), to obtain the selection requirements for the amplifier;

[0024] Step S323, according to the selection requirements of the amplifier, the signal source transmission frequency f0(n) corresponding to the dynamic matching power P in (n) is obtained.

[0025] Further, the step S4 comprises:

[0026] Step S41, initializing n=1, after building the reference level measurement system, the frequency sweep bandwidth, the number of scanning points in the frequency sweep bandwidth, the resolution bandwidth, the video filter bandwidth and the frequency sweep time of the signal analyzer are re-set again;

[0027] Step S42, the transmission power corresponding to the signal source transmission frequency f0(n) is set as the dynamic matching power P in (n), the center frequency of the signal analyzer is set as the frequency offset compensated frequency F SA (n), the power value X(n) corresponding to the center frequency of the signal analyzer is measured according to the parameters of the signal analyzer set in step S41; n=1, 2, …, N, N represents the number of test frequency points set when the shielding effectiveness is measured;

[0028] Step S43, n=n+1, return to step S42, until n=N, the reference level CR(N) of the signal analyzer 21 at all test frequency points is obtained.

[0029] Further, the step S5 comprises:

[0030] Step S51, initializing n=1, the frequency sweep bandwidth, the number of scanning points in the frequency sweep bandwidth, the resolution bandwidth, the video filter bandwidth and the frequency sweep time of the signal analyzer are set to be consistent with the set values in step S41;

[0031] Step S52, the transmission power corresponding to the signal source transmission frequency f0(n) is set as the dynamic matching power P in (n), the center frequency of the signal analyzer is set as the frequency offset compensated frequency F SA (n), the power value X'(n) corresponding to the frequency F SA (n) after shielding is measured according to the parameters set in step S51;

[0032] Step S53, n=n+1, return to step S52, until n=N, the power value NF(N) corresponding to all test frequency points after shielding is obtained;

[0033] Step S54, according to the reference level CR(N) and the power value NF(N), the shielding effectiveness SE(N) of the shielding room to be measured is calculated.

[0034] The super high shielding effectiveness measurement method of the present application takes the limit of shielding effectiveness measurement capability as the target, takes the 1dB compression point of the signal analyzer as the benchmark to determine the emission power of the signal source at different test frequencies, realizes the dynamic setting of the emission power of the signal source, solves the frequency offset problem existing in the measurement process, and further realizes the super high performance shielding effectiveness measurement requirement. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 is the flow chart of the super high shielding effectiveness measurement method according to the present application.

[0036] Figure 2 is the structural schematic diagram of the shielding effectiveness measurement system.

[0037] Figure 3 is the structural schematic diagram of the frequency offset measurement system.

[0038] Figure 4 is the structural schematic diagram of the reference level measurement system. DETAILED DESCRIPTION

[0039] The preferred embodiments of the present application are given below in combination with the drawings, and are described in detail.

[0040] As shown in Figure 1 , the super high shielding effectiveness measurement method of the present application comprises the following steps:

[0041] Step S1, a shielding effectiveness measurement system is built, as shown in Figure 2As shown, the shielding effectiveness measurement system of the present application comprises a transmitting device 10, a receiving device 20 and a control device 30, the control device 30 being connected with the transmitting device 10 and the receiving device 20 respectively. The transmitting device 10 comprises a signal source 11, a transmitting antenna 12 and a first photoelectric converter 13. The signal source 11 is connected with the transmitting antenna 12 through a radio frequency cable and connected with the first photoelectric converter 13 through a data transmission line. The transmitting antenna 12 is installed in a shielding chamber to be measured, which is the measurement object of the shielding effectiveness measurement of the present application. The receiving device 20 comprises a signal analyzer 21 and a receiving antenna 22, the signal analyzer 21 being connected with the receiving antenna 22 through a radio frequency cable, and the front end of the receiving antenna 22 is provided with an amplifier 23. The control device 30 comprises a control system 31 and a second photoelectric converter 32, the control system 31 being connected with the second photoelectric converter 32 through a data transmission line, the second photoelectric converter 32 being connected with the first photoelectric converter 13 through an optical fiber and connected with the signal analyzer 21 through a data transmission line. The signal source 11, the signal analyzer 21 and the control system 31 are connected through the second photoelectric converter 32, the control of the signal source 11 and the signal analyzer 21 is completed, and the automatic test is realized. In addition, since the electronic equipment is easy to produce strong electromagnetic interference, the signal source 11, the first photoelectric converter 13 and the signal analyzer 21 are placed in a portable shielding tent to reduce the influence of the self interference of the electronic equipment on the measurement results. In the embodiment, the transmitting antenna 12 and the receiving antenna 22 are set to be 1.5 m away from the ground, and the distance between the transmitting antenna 12 and the receiving antenna 22 is 2 m.

[0042] In order to improve the sensitivity of the signal analyzer 21, the key parameters of the signal analyzer 21, such as the sweep bandwidth and the resolution bandwidth, need to be set as small as possible. Since there is a certain frequency deviation in the signal emitted by the high-precision crystal oscillator used by the signal source 11, and the higher the frequency of the transmitted signal is, the more serious the frequency deviation is, and the smaller the sweep bandwidth is set, the frequency deviation causes the receiving device 20 to not receive the signal, resulting in inaccurate test data. In order to solve the frequency deviation problem between the signal frequency emitted by the signal source and the corresponding received signal frequency of the signal analyzer in the shielding effectiveness measurement system, the frequency deviation in the signal source and the signal analyzer measurement system link needs to be measured.

[0043] Therefore, in step S2, the signal source 11 and the signal analyzer 21 in the shielding effectiveness measurement system 1 are taken out, the frequency deviation between the signal frequency emitted by the signal source 11 and the corresponding received signal frequency of the signal analyzer 21 is measured, and the frequency deviation of the frequency corresponding to all test frequency points set when the shielding effectiveness is measured is compensated.

[0044] Specifically, step S2 comprises:

[0045] Step S21, as Figure 3As shown, the signal source 11 and the signal analyzer 21 taken out from the shielding effectiveness measurement system 1 are directly connected through a radio frequency cable to build the frequency deviation measurement system. The radio frequency cable used satisfies the highest frequency range of the measurement, for example, if the test frequency range of the shielding effectiveness measurement is 10 kHz-18 GHz of the full frequency band, the working frequency band of the radio frequency cable in the frequency deviation measurement system needs to satisfy the working requirement of 18 GHz.

[0046] In step S22, the initial center frequency of the signal analyzer 21 when sweeping and the frequency of the signal source 11 transmitting the signal are both set to f1(m), and the sweeping bandwidth of the signal analyzer 21 is set to 10 kHz.

[0047] Wherein, f1(m) = F source (m), F source (m) = [F1, F2, …, F m , …, F M ], m = 1, 2, …, M, M represents the number of frequency points set when performing the frequency deviation measurement, M = B / S, B represents the frequency deviation measurement bandwidth, B = F z 1, F1 represents the starting frequency of the shielding effectiveness measurement, F z represents the terminal frequency of the shielding effectiveness measurement; S represents the frequency step length set when performing the frequency deviation measurement, S ≦ B / 10; F1 = F1, F2 = F1 + S, …, F M-1 = F1 + MS, F M = F z . The smaller the frequency step length S is, the more the number of frequency points of the frequency deviation measurement is, and the result is more accurate, but the measurement time and workload increase, which can be selected according to the actual measurement requirement.

[0048] The actual receiving frequency of the signal analyzer is measured and recorded at each frequency point, specifically including: when the initial center frequency of the signal analyzer 21 when sweeping and the signal source 11 transmitting the signal are adjusted to a single frequency point in the frequency deviation measurement frequency each time, the actual receiving frequency of the signal analyzer corresponding to the single frequency point of the frequency deviation measurement frequency is recorded by finding and marking the received signal frequency through pressing the “PEAK” and “MARK” keys on the signal analyzer.

[0049] In order to improve the sensitivity of the signal analyzer 21, the sweeping bandwidth Span of the signal analyzer key parameter needs to be set as small as possible. However, considering that when the sweeping bandwidth is set to 10 kHz, all the frequency deviation signals can be observed and recorded in the screen of the signal analyzer 21, if less than 10 kHz, the frequency deviation signal can be out of the screen range of the signal analyzer 21, and the signal cannot be observed, therefore, the sweeping bandwidth of the signal analyzer 21 cannot be infinitely reduced, and the sweeping bandwidth of the signal analyzer 21 is set to 10 kHz.

[0050] Step S23, the frequency offset value f3(m) = f2(m)-f1(m) of each frequency offset measurement frequency point is calculated, f2(m) is the actual receiving frequency of the signal analyzer corresponding to the frequency point f1(m).

[0051] Step S24, the obtained M frequency offset values f3(m) are fitted to obtain a frequency offset curve function. The fitting process is as follows:

[0052] 1) Construct a polynomial fitting output expression as follows:

[0053] F0[f] = a0 + a1f + a2f 2 +…+a k f k

[0054] 2) Establish input sample data as follows:

[0055]

[0056] 3) Establish the equation group:

[0057]

[0058] Let:

[0059]

[0060] 4) Calculate the polynomial coefficient b, and get:

[0061] b = A -1 f

[0062] 5) According to the actual fitting situation, adopt k times polynomial fitting method, and get the frequency offset curve function in the shielding effectiveness measurement frequency band:

[0063] F0[f] = a0 + a1f + a2f 2 +…+a k f k

[0064] Step S25, according to the frequency offset curve function obtained in step S24, the frequency offset compensation is carried out on the frequency corresponding to all test frequency points set when the shielding effectiveness is measured. After frequency offset compensation, the frequency F SA (n) corresponding to the test frequency point set when the shielding effectiveness is measured is calculated according to the following formula:

[0065] F SA (n) = f0(n) + F0[f0(n)]

[0066] In the formula, n = 1, 2, …, N, N represents the number of test frequency points set when the shielding effectiveness is measured, f0(n) represents the signal source transmission frequency corresponding to the nth test frequency point, and the number of test frequency points can be appropriately increased or reduced according to actual test requirements.

[0067] Step S3, after the frequency offset compensation is completed, the 1dB compression point test of the signal analyzer 21 is performed, the 1dB compression point power of the signal analyzer 21 at all test frequency points is obtained, and the dynamic matching power of the signal source 11 at all test frequency points is calculated.

[0068] The 1dB compression point refers to the maximum signal strength that can be processed by the hardware device when processing a signal. When reaching this point, the hardware device will compress the signal to ensure the stability and quality of the output signal. In this embodiment, obtaining the 1dB compression point power of the signal analyzer 21 at all test frequency points includes the following steps:

[0069] Step S311, initialize n = 1, set the step value of the signal source transmission power as ΔP, and reset the sweep bandwidth Span of the signal analyzer 21 as 1kHz, the number of scanning points in the scanning bandwidth is set as 1001, the resolution bandwidth is 10Hz, and the video filter bandwidth is 100Hz. The parameter setting of this step can make the test result more accurate.

[0070] Step S312, for the nth test frequency point, the initial transmission power of the signal source is recorded as P in,0 (n), the initial receiving power of the signal analyzer 21 is recorded as P out,0 (n), and the signal source transmission power is gradually increased according to the step value ΔP. During the gradual increase of the signal source transmission power, the signal source transmission power P in,k (n) is obtained, which satisfies the formula (P in,0 (n)-P out,k (n)-P out,0 (n)) = 1dB + L c (n) when the signal source transmission power P in,k (n) is obtained, thereby obtaining the 1dB compression point power P out,k (n) of the signal analyzer 21 at the frequency point. Wherein, P in,0 (n) = -10dBm, k represents the step number of the signal source transmission power at the nth test frequency point, P in,k (n) represents the output power of the signal source when reaching the 1dB compression point of the signal analyzer at the nth test frequency point; L c (n) represents the cable loss value corresponding to the nth test frequency point.

[0071] Step S313, let n=n+1, return to step S312 until n=N, get the 1dB compression point power of the signal analyzer 21 at all test frequencies, the 1dB compression point power corresponding to the nth test frequency is recorded as P out (n).

[0072] In this embodiment, the calculation of the dynamic matching power of the signal source 11 at all test frequencies includes the following steps:

[0073] Step S321, set the frequency offset compensated frequency F SA (n) as the signal analyzer center frequency and the antenna frequency, set the signal source transmission frequency f0(n) as the amplifier frequency and the radio frequency cable frequency, calculate the input port power P a,in (n) and the output port power P a,out (n) corresponding to the amplifier frequency f0(n).

[0074] The input port power P a,in (n) is calculated as follows:

[0075] P a,in (n) = P max -L bf (n)-L c (n)+2×G a (n)

[0076] In the formula, P max max represents the maximum transmission power of the signal source; L bf (n) represents the radio frequency cable frequency f0(n) corresponding to the radio wave propagation loss value, which is calculated according to the free space radio wave propagation model; L c (n) represents the radio frequency cable frequency f0(n) corresponding to the cable loss value; G a (n) represents the antenna gain corresponding to the antenna frequency F SA (n).

[0077] The output port power P a,out (n) is calculated as follows:

[0078] P a,out (n) = P out (n)+L c (n)

[0079] In the formula, P out (n) represents the 1dB compression point power corresponding to the signal analyzer frequency F SA (n).

[0080] Step S322, according to the input port power P a,in (n) and the output port power P a,out(n), the selection requirement of the amplifier 23 is as follows:

[0081]

[0082] wherein P PA (n) represents the 1dB compression point power of the amplifier 23, G PA (n) represents the amplifier gain of the amplifier 23. And, on the basis of meeting the above selection requirement, the amplifier with the lowest noise coefficient is selected. In this way, the input power of the output signal of the signal source after passing through the measurement link to the signal analyzer can meet the 1dB compression point and the noise is small.

[0083] In step S323, the dynamic matching power P in (n) corresponding to the signal source transmission frequency f0(n) is obtained according to the selection requirement of the amplifier 23. in The dynamic matching power P in (n) corresponding to the signal source transmission frequency f0(n) is calculated according to the following formula:

[0084] P out (n) = P c (n) + 2L bf (n) + L a (n) - 2G PA (n) - G points (n)

[0085] In step S4, the signal source 11 and the signal analyzer 21 are put back into the shielding effectiveness measurement system 1, away from the shielding room to be tested, and the transmitting device 10 and the receiving device 20 are placed in the microwave darkroom to build a reference level measurement system as shown in Figure 4 The reference level of the signal analyzer 21 at all test frequencies is measured. In this embodiment, the transmitting device 10 and the receiving device 20 are placed in a 3m microwave darkroom.

[0086] Specifically, step S4 includes:

[0087] In step S41, n = 1 is initialized, and after the reference level measurement system is built, the sweep bandwidth Span, the number of scanning points C sweep , the resolution bandwidth RBW, the video filter bandwidth VBW and the sweep time T sweep of the signal analyzer 21 are reset.

[0088] The sweep bandwidth Span is set to 1kHz, the number of scanning points C points in the sweep bandwidth is set to 101 in order to reduce the sweep time and increase the efficiency of the measurement system. At the same time, in order to best couple the resolution bandwidth RBW and the video filter bandwidth VBW, the resolution bandwidth RBW, the video filter bandwidth VBW and the sweep time Tsweep satisfies the following formula:

[0089] RBW < VBW, k = 0.2

[0090] where k represents a proportional coefficient, which depends on the type of video filter and the allowed transient response error. In the present embodiment, the resolution bandwidth RBW is set to 10 Hz, and the video filter bandwidth VBW is set to 100 Hz, so that the sweep time T sweep is 200 ms.

[0091] In step S42, the transmission power corresponding to the signal source transmission frequency f0(n) is set as the dynamic matching power P in (n), and the signal analyzer center frequency is set as F SA (n). The power value X(n) corresponding to the signal analyzer center frequency F SA (n) is measured according to the parameters of the signal analyzer 21 set in step S41. The power value X(n) corresponding to the frequency F SA (n) is calculated according to the following formula:

[0092] X(n) = MAX[X0(F SA (n)), X1(F SA (n)), X2(F SA (n)), …, X 100 (F SA (n))

[0093] where X0(F SA (n)) represents the power value obtained by the first scan within the sweep bandwidth, X1(F SA (n)) represents the power value obtained by the second scan within the sweep bandwidth, …, X 100 (F SA (n)) represents the power value obtained by the 101st scan within the sweep bandwidth. That is, the power value X(n) corresponding to the frequency F SA (n) is ensured to be the maximum value.

[0094] In step S43, n = n + 1 is set, and the process returns to step S42 until n = N, so as to obtain the reference level CR(N) of the signal analyzer 21 at all test frequencies, i.e.:

[0095]

[0096] In step S5, the microwave darkroom is left, and the shielding chamber under test is returned. The power values corresponding to all test frequencies after shielding are measured, and the shielding effectiveness of the shielding chamber under test is obtained according to the reference level obtained in step S4.

[0097] Specifically, step S5 includes:

[0098] Step S51, initialize n=1, set the signal analyzer 21 sweep bandwidth Span, the number of scanning points C within the sweep bandwidth, resolution bandwidth RBW, video filter bandwidth VBW and sweep time T points , consistent with the set value in step S41. sweep

[0099] Step S52, set the signal source transmission frequency f0(n) corresponding to the transmission power for dynamic matching power P in (n), set the signal analyzer center frequency for F SA (n), according to the parameters set in step S51, measure the power value X'(n) corresponding to the frequency F SA (n) after shielding. The power value X'(n) corresponding to the frequency F SA (n) after shielding is calculated according to the following formula:

[0100] X'(n)=MAX[X0'(F SA (n)),X1'(F SA (n)),X2'(F SA (n)),…,X 100 '(F SA (n))]

[0101] Step S53, n=n+1, return to step S52, until n=N, get the power value NF(N) corresponding to all test points after shielding, that is:

[0102]

[0103] Step S54, according to the reference level CR(N) of the signal analyzer 21 at all test points and the power value NF(N) corresponding to all test points after shielding, calculate the shielding effectiveness SE(N) of the shielding room to be tested, that is:

[0104]

[0105] The above is only the preferred embodiment of the present application, not to limit the scope of the present application, the above embodiment of the present application can be made various changes. That is, according to the content of the present application claims and description of the simple, equivalent changes and modification, all fall within the scope of the present application patent claims. The present application is not described in detail, all are conventional technical content.​

Claims

1. A method for measuring ultra-high shielding effectiveness, characterized in that, include: Step S1: Construct a shielding effectiveness measurement system, which includes a transmitting device, a receiving device, and a control device connected to the transmitting device and the receiving device. The transmitting device includes a signal source, a transmitting antenna connected to the signal source, and a first photoelectric converter connected to the signal source. The transmitting antenna is installed in the shielded room to be tested. The receiving device includes a signal analyzer and a receiving antenna connected to the signal analyzer, and an amplifier is provided at the front end of the receiving antenna; the control device includes a control system and a second photoelectric converter connected to the control system, the second photoelectric converter being connected to the first photoelectric converter and to the signal analyzer. Step S2: Take out the signal source and the signal analyzer, measure the frequency deviation between the frequency of the signal transmitted by the signal source and the frequency of the corresponding received signal by the signal analyzer, and perform frequency offset compensation on the frequencies corresponding to all test frequency points set during the shielding effectiveness measurement to obtain the frequency after frequency offset compensation. Step S3: After completing frequency offset compensation, perform a 1dB compression point test on the signal analyzer, obtain the 1dB compression point power of the signal analyzer at all test frequencies, and calculate the dynamic matching power of the signal source at all test frequencies; wherein, obtaining the 1dB compression point power of the signal analyzer at all test frequencies includes: Step S311, Initialization 1. Set the step value of the signal source's transmission power to Δ And reset the sweep bandwidth, number of scan points within the sweep bandwidth, resolution bandwidth and video filter bandwidth of the signal analyzer; Step S312, for the first The initial transmit power of the signal source at each test frequency point is denoted as . The initial received power corresponding to the signal analyzer is denoted as . According to the step value Δ Gradually increase the signal source's transmission power, and obtain the result satisfying the formula during the gradual increase of the signal source's transmission power. The corresponding signal source transmission power Thus, the 1dB compression point power of the signal analyzer at that frequency can be obtained. ;in, Indicates the first The number of steps in the signal source's transmit power at each test frequency. Indicates the first The output power of the signal source when the signal analyzer reaches the 1dB compression point of the signal analyzer at each test frequency; Indicates the first The cable loss value corresponding to each test frequency point; , This indicates the number of test frequencies set when measuring shielding effectiveness; Step S313, let = +1, return to step S312, until... = The 1dB compression point power of the signal analyzer at all test frequencies was obtained. The 1dB compression point power corresponding to each test frequency point is denoted as . ; Step S4: Return the signal source and the signal analyzer to the shielding effectiveness measurement system, leave the shielded room under test, and place the transmitting device and the receiving device in a microwave anechoic chamber to set up a reference level measurement system and measure the reference level of the signal analyzer at all test frequencies; including: Step S41, Initialization 1. After setting up the reference level measurement system, reset the sweep bandwidth, number of scan points within the sweep bandwidth, resolution bandwidth, video filter bandwidth, and sweep time of the signal analyzer. Step S42: Set the signal source transmission frequency The corresponding transmit power is the dynamic matching power. Set the center frequency of the signal analyzer to the frequency after frequency offset compensation. According to the parameters of the signal analyzer set in step S41, the power value corresponding to the center frequency of the signal analyzer is measured. ; , This indicates the number of test frequencies set when measuring shielding effectiveness; Step S43, let = +1, return to step S42, until... = The reference level of the signal analyzer at all test frequencies is obtained. ; Step S5: Leave the microwave anechoic chamber, return to the shielded chamber under test, measure the power values ​​corresponding to all test frequencies after shielding, and obtain the shielding effectiveness of the shielded chamber under test based on the reference level; including: Step S51, Initialization 1. Set the sweep bandwidth, number of scan points within the sweep bandwidth, resolution bandwidth, video filter bandwidth, and sweep time of the signal analyzer to be consistent with the settings in step S41. Step S52: Set the signal source transmission frequency. The corresponding transmit power is the dynamic matching power. Set the center frequency of the signal analyzer to the frequency after frequency offset compensation. The frequency after shielding is measured according to the parameters set in step S51. Corresponding power value ; Step S53, let = +1, return to step S52, until... = The power values ​​corresponding to all test frequencies after shielding were obtained. ; Step S54, according to the reference level and the power value Calculate the shielding effectiveness of the shielded room under test. .

2. The method for measuring ultra-high shielding effectiveness according to claim 1, characterized in that, Step S2 includes: Step S21: Connect the extracted signal source and the signal analyzer directly through an RF cable to build a frequency offset measurement system; Step S22: Sequentially set the initial center frequency of the signal analyzer and the frequency of the signal emitted by the signal source to the frequencies corresponding to the frequency offset measurement points. The sweep bandwidth of the signal analyzer is set, and the actual receiving frequency of the signal analyzer is recorded at each frequency offset measurement point; wherein, , This indicates the number of frequency points set when performing frequency offset measurement; Step S23: Calculate the frequency offset value at each frequency offset measurement frequency point. , For frequency point The actual receiving frequency of the corresponding signal analyzer; Step S24, obtain Individual frequency deviation Perform fitting to obtain the frequency offset curve function; Step S25: Based on the frequency offset curve function, perform frequency offset compensation on the frequencies corresponding to all test frequency points set during the shielding effectiveness measurement to obtain the frequency after frequency offset compensation. , , This indicates the number of test frequencies set when measuring shielding effectiveness.

3. The method for measuring ultra-high shielding effectiveness according to claim 1, characterized in that, The calculation of the dynamic matching power of the signal source at all test frequencies in step S3 includes: Step S321, adjust the frequency after frequency offset compensation. Set the signal analyzer's center frequency and antenna frequency, and set the signal source's transmission frequency. Set the amplifier frequency and RF cable frequency to calculate the amplifier frequency. Corresponding input port power and output port power ; Step S322, based on the input port power and the power of the output port To obtain the selection requirements for the amplifier; Step S323: Obtain the signal source transmission frequency according to the amplifier selection requirements. Corresponding dynamic matching power .

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