Research on white noise immunity test method of CISPR35(GBT9254.2)_Century Wisdom (Suzhou) Testing Technology Co., Ltd

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Research on white noise immunity test method of CISPR35(GBT9254.2)

Release time:

2023-08-21 15:45

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　　1 Introduction

CISPR 35(GBT9254.2) has added a new immunity test item for EUT's xDSL(X-type digital subscriber line) port: broadband pulse conduction disturbance immunity. The repetitive noise pulse and the isolated noise pulse are separately applied to the xDSL port of the EUT. This test procedure is based on the CDN method specified in IEC61000-4-6:2008, but the signal generator is replaced with a generator that can generate white noise pulses. See the following figure:

　　2 Introduction to the test

　　2.1 test grade

The following table gives the requirements for the test class, pulse duration and pulse period for both tests.

A. For repeated pulse test, each test port shall be harassed for at least 2min.

B. For the isolated pulse test, at least 5 isolated pulses shall be applied, and the interval between each pulse shall be at least 60s.

　　2.2 test equipment

2.2.1 White noise pulse source

The white noise pulse source comes from a long sequence pseudo-random near-Gaussian white noise generator, which has the following characteristics:

A, generated by an arbitrary waveform generator, the length of the resulting noise pulse group sequence should contain at least 128k samples.

B. Frequency range from 150kHz to the highest frequency used by xDSL technology or 30MHz, whichever is the lowest

C, white noise needs to be pulse modulated and injected into CDN in the form of pulses

To sum up, the white noise source can replace the analog signal source in the IEC61000-4-6 with a vector signal source, such as a SMCV100B.

Note 1:

Analog source: mainly produces single frequency signal, sweep signal, RF pulse (single or double pulse), AM/FM/PM analog modulation signal, but can not produce PSK/QAM and other digital modulation signal.

Vector source: basically contains all the functions of analog sources, and also supports the generation of general digital modulation signals such as PSK/QAM, as well as complex radio frequency pulse signals such as chirp pulse and Barker code pulse.

2.2.2 Power Amplifier

A. The power amplifier and CDN used in the system shall have a frequency response that does not change more than 3dB within the test frequency range.

B, the frequency range should at least include 150kHz ~ 30MHz

C at the input port of CDN (output port of power amplifier), the ratio of peak value to effective value of signal should be at least 4.0

In summary, recommend use BBA150 A125 solid state power amplifier

2.2.3 Coupling Decoupling Network/CDN

A, suitable for xDSL(X type digital subscriber line) port

B, CDN in the relevant frequency range should have at least 60dB LCL

C at the input port of CDN, the ratio of the peak value to the effective value of the signal should be at least 4.0.

D. The amplifier and CDN used should have a frequency response that does not exceed 3dB in the frequency range.

In summary, the CDN should be CDN T2.

2.2.4 Monitoring Ports

The monitoring port includes the forward and reverse power monitoring of the power amplifier, and the monitoring port for feedback of the calibration waveform test level during calibration.

A, the power amplifier's forward and reverse power monitoring probe, using the average power meter probe NRP 6A(NRP 6AN)

B. The monitoring port that feeds back the test level of the calibration waveform during calibration uses a spectrum analyzer with a resolution bandwidth (RBW) of 10kHz and a video bandwidth (VBW) less than or equal to 10Hz to set the specified test level in the peak detection mode. So use an oscilloscope or spectrum analyzer (receiver)

　　Introduction to 2.3 Test Layout

2.3.1 Schematic diagram of test connection

Using the IEC61000-4-6:2008 the arrangement shown in FIG. 8c, the test signal generator is adjusted so that a given level is reached at the EUT port of the CDN.

　　2.4 Test/Calibration Considerations

Using a spectrum analyzer with a resolution bandwidth (RBW) of 10kHz and a video bandwidth (VBW) of less than or equal to 10Hz, set the specified test level in peak detection mode.

Note 2:

The relationship between the measurement level (M) in dBμV and the test level (T) in dBμV given in the table is as follows:

　　M =T -27.6dB

In the formula:

　　27.6dB=A1 A2 A3;

A1 = 9.6dB(150 Ω/50Ω conversion loss);

A2 = 6dB (EMF correction, signal generator output is terminated at 50Ω);

A3 = 12dB video bandwidth (VBW) reduction caused by the average effect.

Note 3:

The test level of the xDSL line is derived from the power spectral density (dBm/Hz) of-43dBm/Hz,

Test level (dBμV)= power spectral density (dBm/Hz) 150dB

In the formula:

　　150dB=A1 A2 A3;

A1 = 40dB(10kHz bandwidth factor);

A2 =-10dB (for 100Ω impedance mW to V conversion);

A3 = 120dB(V to μV conversion).

　　Determination of 2.5 test results

2.5.1 Wideband impulse noise disturbance (repetition)

The impulse noise protection (INP) level supported by the EUT is selected for the immunity test, and the level used is specified in the test report. The maximum delay shall be set to 8ms.

When pulse disturbance is not applied: The modem should not retrain within the noise index margin related to the transmission rate. The transmission rate depends on the line attenuation and the line steady-state noise (the actual value is between the minimum and maximum transmission rate preset by the port).

Then apply the pulse disturbance according to the required test level.

When pulse disturbance is applied: the modem shall not be retrained, there shall be no serious error seconds, and it shall work at the transmission rate established before pulse disturbance is applied. The resulting additional error does not exceed 5% of the static level.

2.5.2 Wideband impulse noise disturbance (isolated)

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