Overview of automotive electronic radio frequency immunity test methods-anechoic chamber method_Century Wisdom (Suzhou) Testing Technology Co., Ltd

English

Home page

Technical column

CASES

Overview of automotive electronic radio frequency immunity test methods-anechoic chamber method

Release time:

2023-03-27 15:14

Source:

　　Overview of automotive electronic radio frequency immunity test methods-anechoic chamber method

1 Foreword

The anechoic chamber method introduced in this paper is mainly applied to the RF immunity test in the frequency range of 80MHz ~ 18GHz. The advantage of the anechoic chamber method is that it can analyze the immunity characteristics of almost all auto parts and devices in the radio frequency range of 80MHz to 18GHz, and it is aimed at including the main parts of the tested sample, the wiring harness, the auxiliary device and the like. Analysis of the entire system.

2 Test methods

The RF immunity test method is an electromagnetic compatibility immunity test method that must be completed in an anechoic chamber. The anechoic chamber is designed to provide a place to isolate electromagnetic waves and to simulate open field testing. The main structure of the anechoic chamber is mainly a shielding room and a wave-absorbing material. The purpose of the design is to make the reflected energy in the test area at least lower than the energy in the direct emission direction. The shielding room is composed of shielding shell, shielding door, ventilation waveguide window and various power filters. The radio frequency electromagnetic field in the anechoic chamber is generated by a radio frequency source capable of generating radio frequency signals of different levels through a transmitting antenna.

Fig. 1 Test Site

The test levels are as follows:

Fig. 2 Test Grade

Each port of the tested article shall be terminated with a typical load, and other working conditions shall be consistent with those on the vehicle.

Antenna horizontal polarization direction test frequency range: 400MHz ~ 18GHz;

Antenna vertical polarization test frequency range: 80MHz ~ 18GHz;

The ISO 11452-2 standard states that the test should be performed using an alternative method, based on the forward power as a reference parameter during field calibration and testing. It is carried out in two stages:

a) Field calibration (without EUT, harness and peripherals)

For a specific test level (field strength), it should be calibrated periodically, and for each test frequency point, the forward power required to produce a specific field strength (measured by the field strength probe) should be recorded. An unmodulated sine wave should be used for calibration.

Place the center point of the field strength probe at (150±10)mm above the ground plane and (100±10)mm from the edge of the ground plane. For the frequency range of 80MHz-1GHz, the field strength probe should be placed at the center of the wire harness (1.5 m long). For the frequency above 1GHz, the field strength probe should be placed at DUT, and the field strength generator (antenna) should be placed at (1000±10)mm from the center of the field strength probe.

The field strength is calibrated separately for vertical polarization and horizontal polarization, the forward power and reverse power are recorded, and the precise position of the field strength probe is stated in the test report.

B) Test the EUT (connect harness and peripherals)

Place the EUT on the test table and connect the harness and related equipment, apply the test signal obtained during calibration to the DUT, and place the field probe above the harness during the test phase.

For each frequency point, horizontal polarization and vertical polarization tests are performed separately.

Fig.3 Schematic diagram of calibration test configuration of free-field test system composed of three power amplifiers

3 Test equipment

The radiated electromagnetic field is formed using an antenna and a radio frequency (RF) energy source that generates the required field strength. Need a set of antenna, amplifier, RF signal generator, can cover the test frequency range. In order to ensure the test level, the field strength probe is used to determine the electromagnetic field strength required for the test. In order to reduce the test error, the working state of the tested product is usually monitored by the photoelectric coupler.

The main test equipment includes:

A, antenna: need to meet the frequency range required for the test, while meeting the power requirements required for the test

Figure 4 Antenna

B, field strength probe

Fig. 5 Field Strength Probe

C, signal generator: need to meet the test required frequency range, with modulation function

Fig. 6 Signal Generator

D, power amplifier: need to meet the frequency range required for the test, while meeting the power requirements required for the test

Figure 7 Power Amplifier

E, power meter: used to test the power amplifier forward power and reverse power

Figure 8 Power Meter

F, Artificial Power Network (AN)

Figure 9 Artificial power network

Fig. 10 System connection diagram

4 Test arrangement

The key to affect the test results of the anechoic chamber method is the test layout, including the ground plate, the location of the tested piece, the layout of the test harness, the layout of the simulated load and the layout of the antenna.

Requirements for grounding plate: the grounding plate shall be copper, brass or galvanized steel plate with a thickness of at least 0.5mm. The minimum width is 1000mm and the minimum length is 2000mm, or 200mm larger than each side of the tested article, and the larger grounding plate of the two is taken. The height of the grounding plate (test bench) shall be placed at (900±100)mm above the ground. The grounding plate shall be electrically lapped with the shell of the shielding room. The DC resistance shall not exceed 2.5 mΩ, and the distance between the grounding strips shall not be greater than 0.3m.

The power cord of the tested product is connected to the power supply through. The AN is directly installed on the grounding plate, and the shell is lapped with the grounding plate. The measurement port of each AN is terminated with a 50Ω load.

The position of the tested product is required to be placed on an insulating material with a low dielectric constant (εr ≤ 1.4), 50±5mm higher than the ground plate. Unless it is for actual loading conditions, the shell of the tested article is not connected with the grounding plate, and each surface of the tested article shall be 200±10mm away from the edge of the grounding plate.

The test harness layout stipulates that the part of the test harness parallel to the front edge of the ground plate is 1500±75mm. The total length of the test harness between the test item and the simulated load shall not exceed 2000mm. The type of wire harness is defined by the actual system and requirements. The test wire harness is placed on a non-conductive, low relative dielectric constant material, 50±5mm higher than the ground plate. The part of the test harness parallel to the front edge of the ground plate is 100±10mm from the edge of the ground plate.

Simulated load arrangement: The simulated load is suitably placed directly on the ground plate. If the simulated load has a metal housing, the housing is connected to the ground plate. The simulated load can be placed on the ground plate or in a dark room, and the test harness provided is connected to the ground plate from the tested part through the wall. When the simulated load is placed on the ground plate, the DC power lines of the load are connected to the power supply through the artificial power supply network.

Arrangement of the antenna: The phase center of the antenna is 100±10mm above the ground plane. Any radiating part of the antenna shall not be less than 250mm from the floor. Any transmitting part of the antenna shall not be less than 500mm from any wave absorbing material, and shall not be less than 1500mm from the wall or top of the shielding shell. The distance between the test harness and the antenna is 1000±10mm.

The test layout is shown in Fig. 11 ~ Fig. 13.

Fig. 11 Layout of Biconical Antenna Test

Fig. 12 Layout of Log Periodic Antenna Test

Fig. 13 Horn Antenna Test Layout

5 Actual Layout

The following is the actual layout:

Fig. 14 Actual Layout

Century Wisdom (Suzhou) Testing Technology Co., Ltd

www.300.cn nanjing SEO

Business License

全部

全部
产品管理
新闻资讯
介绍内容
企业网点
常见问题
企业视频
企业图册