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How to use Rigol spectrometer for EMI pre-compatibility testing, in view of this problem, this article introduces the corresponding analysis and solution in detail, hoping to help more partners who want to solve this problem to find a more simple and feasible method.

There are two types of spectrum analyzer: frequency sweep and real-time. Frequency sweep spectrometer is the most common spectrum analyzer, which uses local oscillator scanning to test the frequency, power and other parameters of the signal in the test range. The real-time spectrum analyzer is in a fixed bandwidth through real-time data acquisition and FFT analysis to get the amplitude and frequency parameters of the signal within the bandwidth range, and the speed is hundreds or even thousands of times higher than that of frequency sweep. Mainly consider the test frequency range, power range, test speed, signal frequency resolution requirements, signal size and other factors. Because of the frequency range of the spectrometer, DANL,RBW, test speed and other considerations.

Electromagnetic compatibility (EMC) refers to the ability that the equipment or system meets the requirements in its electromagnetic environment and does not cause unbearable electromagnetic interference to any equipment in its environment. Therefore, EMC includes two aspects: electromagnetic interference (EMI) and electromagnetic anti-interference (EMS). The specific categories are as follows:

With the increase of the application of electronic products, the electromagnetic environment around us is becoming more and more complex, and the impact on our work and life is becoming closer and closer. For example, the high-frequency signal lines in high-speed PCB, the pins of integrated circuits and all kinds of connectors may become radiation interference sources, which will affect the normal work of other systems or other subsystems in this system.

Similar to the radars and antennas on warships, they have electromagnetic compatibility problems with each other.

EMC standard

In order to ensure that electronic products meet the requirements of reliability in the electromagnetic environment, countries have formulated EMC regulations on electronic products according to international standards, requiring products to be sold in the country only after they have been certified. Our country mainly imitates the European standard and establishes the national standard, 3C certification, including the well-known automobile emission standard.

IEC (International Electrotechnical Commission) is the earliest international electrical standardization organization in the world, which is responsible for international standardization in the field of electrical and electronic engineering. The main organizations engaged in the formulation of EMC standards are CISPR (International Special Committee on Radio interference) and TC77 (Technical Committee 77). IEC standard has been widely adopted in Europe, the United States, Japan, China and other regions and countries. The related certifications are CE certification of EU, FCC certification of USA, 3C certification of China and so on.

Introduction to EMI testing

EMI (ElectromagneticInterference, electromagnetic interference) is a phenomenon that can transmit electromagnetic interference through space (radiation) or AC lines (conduction), affecting the normal operation of electrical and electronic circuits. There are two kinds of conducted interference and radiation interference.

Conducted interference: means to connect an electric network through a conductive medium (power cord, external cable, etc.)

The signal is coupled (interfered) to another electrical network.

Radiation interference: refers to the interference source coupling its signal to another power grid through space.

Collaterals.

High-frequency electromagnetic waves mainly propagate on the surface of conductive media and are easy to interfere with another electrical network through space.

Classification of equipment under test

Category An equipment: non-domestic and equipment not directly connected to residential low-voltage power supply facilities (industrial and commercial)

Class B equipment: household equipment and equipment directly connected to residential low-voltage power supply facilities.

Test receiver geophone requirements

Due to the difference between broadband and narrowband responses of disturbance sources, quasi-peak and average geophone receivers are generally required for measurement (when the test result of peak geophone is large, the standard geophone measurement shall prevail).

RBW requirements for quasi-peak geophones

Basically, the interference is very small when it comes to 1GHz.

Conducted interference CE

The conducted interference is mainly at the frequency below 30MHz. For the conducted interference of the power terminal, it mainly measures the disturbance voltage transmitted by the tested equipment to the power supply network along the power line, and also includes the disturbance signal transmitted to other connected peripheral equipment through the signal line. Conducted interference testing equipment mainly includes artificial power network (AMN), usually can be replaced by LISN, limiter and spectrum analyzer (quasi-peak detector, 6dB EMI filter).

The function of the limiter is to worry that the electromagnetic radiation of the EUT is too strong and affect the spectrum itself, so add a limiter in the network for protection. For example, products that simulate high voltage and lightning tests usually add a limiter.

The role of artificial Power Network (AMN)

Isolation and coupling effect: prevent the RF electromagnetic disturbance generated by EUT from entering the power grid and attenuate at the same time.

Interference signal from the power grid; connects the radio frequency disturbance signal to the measuring receiver by coupling capacitance

2music-> stable impedance function: provide a unified impedance (50 Ω) to facilitate test junctions in different power grids

Compare the results with each other.

Classification of AMN

There are two types of AMN: v for coupling asymmetric voltages and delta for coupling symmetrical and asymmetric voltages. Linear Impedance Stabilization Network (LISN) and V-type artificial power network can be used interchangeably.

Symmetrical voltage: the RF disturbance voltage between two wires, often referred to as differential mode voltage. Va-Vb

Asymmetric voltage: the RF voltage between the electrical midpoint of two wires and the reference ground, also known as common-mode voltage. (Va + Vb) / 2

Asymmetric voltage: the voltage between a wire or terminal and a specified grounding reference. Va & Vb

Laboratory test environment Class B equipment power supply terminal disturbance voltage limit

This figure takes the national standard of the power terminal product as an example, the instrument has built-in the standard of two kinds of products, and the test only needs to be selected.

The frequency spectrum is very good in the low frequency dynamic range, so the conduction test is mainly based on power products.

The RSA3000E series shows that the average noise level is as low as-161dBm, which can effectively ensure the testing ability of weak signals.

The host computer software of S1210--EMI pre-conformance test should be installed during the test. RSA3000E series spectrum built-in EMI prediction application software, combined with CISPR standard filter, the product conduction and radiation pre-test, so as to find its conduction / radiation disturbance source and improve.

Built-in CISPR bandwidth and detector

Automatically scan multiple segments

Limit line and automatic peak / limit search

Up to 3 traces using different detectors

Recording frequency display

Use three detectors to make real-time measurements on marked or interesting signals

Correction of antennas, LISN, cables and preamplifiers

The actual test architecture of conducted interference CE is as follows

Radiation interference RE test

When the frequency is higher than 30MHz, radiation becomes the main mode of propagation. The testing is generally divided into certification testing and pre-testing. Certification testing needs to be carried out in an open field or anechoic chamber, and the measuring distance of civilian products is generally divided into 3m, so the input cost is very expensive. Therefore, the potential problems are usually solved mainly by using predictive testing in the design stage. The electromagnetic radiation prediction test equipment mainly includes spectrum analyzer (quasi-peak detector, 6dB EMI filter), power amplifier and near-field probe.

Power amplifier: mainly used to amplify the power of the radiation signal into the spectrum analyzer. (usually connected to the back of the probe)

Near-field probe: used to receive and transmit magnetic field radiation signals in the circuit.

There are many types of near-field probes, which can be selected according to the needs of the actual products.

NFP-3-P1, magnetic field near-field probe, can detect magnetic field in the range of 10cm, which is suitable for detecting leaking magnetic field. For example, the verification of shielding measures, chassis leakage testing and so on.

NFP-3-P2, magnetic field near-field probe, can detect the magnetic field in the range of 3cm, which is suitable for the magnetic field environment near the detection module. For example, accurately locate the leakage location of the chassis, detect the magnetic field direction and intensity of the circuit board module and so on.

NFP-3-P3, magnetic field near-field probe, resolution about 5mm, suitable for detecting surface magnetic field. For example, the magnetic field produced by wires, cables, metal surfaces, connectors, electronic components, connections of components, etc.

NFP-3-P4, a magnetic field near-field probe with a resolution of about 2mm, can detect the magnetic field emitted in the vertical direction, which is suitable for detecting the magnetic field produced by the current loop. Such as PCB wiring electromagnetic field test, IC pin area magnetic field detection and so on.

Radiation test example:

This is the answer to the question on how to use the Rigol spectrometer for EMI pre-compatibility testing. I hope the above content can be of some help to you. If you still have a lot of doubts to be solved, you can follow the industry information channel for more related knowledge.

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