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Comparative analysis of DO-160G and DO-160F in EMC

  On December 8, 2010, Special Committee 135(SC135) of the U.S. Space Radio Technology Committee (RTCA) announced the official release of the DO-160G and the inactivation of the DO-160F. Before that, SC135 had released six versions of A, B, C, D, E and F for DO-160. DO-160G stipulated the test level and limit requirements of all aerospace equipment at the present stage, which is not only applicable to general spacecraft, helicopter, commercial jet aircraft and jumbo jet aircraft. It is also suitable for European Airlines A350XWB and Boeing 747-8.

  DO-160G is equivalent to the European Union standard ED-14G, which specifies the environmental requirements and test methods for airborne equipment. It consists of 26 chapters and 3 appendices, with chapters 1 to 3, 15 to 23, and 25 covering EMC. This standard specifies requirements and test methods for airborne equipment in terms of temperature, vibration, salt spray, power input, radio frequency sensitivity, lightning, electrostatic discharge, etc. The following is a comparative analysis of DO-160G and DO-160F involving electromagnetic compatibility, to elaborate the new requirements of DO-160G for airborne equipment and test methods, in order to design a reasonable test scheme for the current airborne equipment.

  1 Analysis of each chapter

  1.1 The first three chapters

  Chapter 1 Test purpose and applicability, Chapter 2 definition of terms, chapter 3 test conditions. These three chapters provide reference for the following chapters and provide detailed guidance for specific tests. In the DO-160G, Chapter 1 emphasizes the importance of the user manual in the appendix; In Chapter 2, the classification of test equipment is explained in detail. In particular, it is pointed out in 2.8 that when the equipment belongs to a special class, it only needs to follow the class with lower requirements in the test. Chapter 3 describes the configuration of the EUT sensitivity test, with special emphasis on EUT curing software and general software operating as required during the test.

  1.2 Chapter 15 Magnetic Field Effects

  To verify the impact of the magnetic field generated by the EUT on the environment, the size of the magnetic field is indicated by a compass pointer or magnetic probe, also known as the "magnetic valve". During the test, the EUT is gradually approached to the standard compass along the east-west line until the observation pointer is offset by one degree, and the spacing is measured to determine the "equipment classification". The equipment is classified into 5 classes (Y, Z, A, B, and C) based on spacing from less than 30cm to more than 300cm. In DO-160G, modify the test configuration as shown in Figure 15-1 to determine the distance between the compass and the device under test when the compass pointer is offset by 1°, thus determining the device grade.

  1.3 Chapter 16 Power Input

  Although MIL-STD-704F, GJB 181A-2003 and GB 17626.11-2008 have discussed the electromagnetic compatibility test of power supply characteristics, there are great differences in the test signal, EUT state and test methods imposed by various standards on EUT. In the DO-160G, when the AC or DC power supply changes in different conditions, test the on-board equipment can work as required under normal and emergency conditions. This part divides the equipment into four categories (A, B, D, Z). For AC power supply equipment, it is further divided into fixed frequency (CF), narrow frequency conversion (NF) and wide frequency conversion (WF).

  Due to the continuous development of aircraft power systems, this section has undergone major modifications in the last 10 years. In DO-160E, for ease of use and understanding, this chapter is divided into two parts of DC and AC test, and adds the influence of load equipment on aircraft power system and DC test items of AC power supply equipment. DO-160G to add 270V DC power system test project. In DO-160G, the test of equipment powered by multiple sources, short-time interrupt of AC power supply equipment, each phase surge test of three-phase AC power supply equipment, Table 16-1, 16-2, 16-3, voltage error of test signal source are modified.

  1.4 Voltage Spikes in Chapter 17

  When the interference signal is output to the EUT power input port through the signal source with an output impedance of 50Ω for 1min, test whether the equipment works properly during and after the test as required. The interference signal is the peak voltage whose rise time is less than 2ms and duration is more than 10ms. This test method is similar to CS106 in MIL-STD-461F. In this chapter, EUTs are divided into two classes (A, B). The test voltage of Class A is 600V, and the test voltage of Class B is twice the effective value of AC, or twice the DC voltage, or the sum of both, with a maximum value of 200V(see Figure 1). In DO-160G, the signal source is specified to produce at least 50 positive and 50 negative spikes during the test.

Figure 1 Voltage peak waveform

  1.5 Chapter 18 Power Cable Audio Conduction Sensitivity

  The test method is similar to CS101 in MIL-STD-461F, the test frequency is 10Hz ~ 150kHz, the test voltage is divided into several stages of different sizes according to the test frequency, the frequency step of the scan is 30(every 10 octaves), and the duration of each frequency is 1min. In this part, DC power supply equipment is divided into 3 categories (R, B, Z) and AC power supply equipment into 2 categories (R, K). Among them, K includes 3 categories: fixed frequency (CF), narrow frequency conversion (NF) and wide frequency conversion (WF).

  DO-160G puts the notes and remarks at the end of the DO-160F in the new user manual section; Delete the limit value of 100W output power of the test signal, and use the current limit with a peak value of 36A; Modified test layout to allow for "optional AC current monitoring" in place; Delete the requirement that the output impedance of the coupling transformer be 0.6Ω.

  1.6 Sensing Signal sensitivity in Chapter 19

  In this section, EUTs are divided into four categories (A, B, C, Z) for devices and interconnection cables to function as required when they are affected by audio electric and magnetic fields and transient voltage spikes. For AC power supply equipment, it can be divided into fixed frequency (CF), narrow frequency conversion (NF) and wide frequency conversion (WF) according to the working frequency. Adding C, N, or W to the first four types of characters is the corresponding type of AC power supply equipment. Test frequency is determined according to the type of equipment, different equipment types, test frequency range is different. The frequency sweep rate is 30(every 10 octave), and the frequency stops for 10s.

  The DO-160G clarifies that the test does not apply to power input cables or wires; Add the "electric field induction of equipment" test, apply a single RMS voltage of 400Hz of 170V to all equipment, and add the corresponding test configuration diagram; Add the switch transient induction test diagram, the peak signal amplitude can vary during the test, and can be less than 600Vpp.

  1.7 Chapter 20 Radio-frequency Sensitivity (Conduction and Radiation)

  This chapter covers the testing of conduction sensitivity and radiation sensitivity. The interference signals applied to the EUT during the test are continuous wave, square wave amplitude modulation signal and pulse modulated signal. For the test configuration, a linear impedance stabilization network was required to be cascaded between the power line and the EUT, and a 10µF capacitor was connected to ground on each power line. Unless otherwise specified, the length of the interconnection cable should be greater than 3.3m and the length of the power cable should be less than 1m. Figure 2 shows the test configuration of radiation sensitivity.

  The test method of conduction sensitivity is similar to that of CS114 in MIL-STD-461F. Here, EUT is divided into 7 different classes, the test frequency is 10kHz ~ 400MHz, and two scans are required, one is continuous wave and the other is square wave amplitude modulation signal. The radiation sensitivity test method is similar to that of RS103 in MIL-STD-461F. Euts are divided into 10 classes with test frequencies ranging from 100MHz to 18GHz, and the distance between the transmitting antenna and EUT is required to be 1m.

  The DO-160G has an added user manual; Each surface of the EUT is required to be exposed to the same amount of radiation, and the surface that cannot be performed should be indicated in the test report; It is clarified that the distance between the test antenna and EUT should be consistent with that during calibration.

FIG. 2 Configuration of radiation sensitivity test


  1.8 Chapter 21 Radio-frequency Energy Emission

  The radiofrequency (RF) emission signals of EUT are tested with peak detection, including conduction emission and radiation emission. In this chapter, EUTs are divided into 6 classes (B, L, M, H, P, Q). The test configuration requires a linear impedance stabilized network to be connected between the power line and the EUT, and a 10μF capacitor is connected to the ground on each power line. Unless otherwise specified, the length of the interconnection cable should be greater than 3.3m and the length of the power cable should be less than 1m. The test frequency is 150kHz ~ 152MHz. During the test, the current probe is stuck on the power line and interconnection cable, and the distance between the probe and EUT is 5cm. The test frequency is 100MHz ~ 6GHz, and the linearly polarized antenna is used to conduct the test in horizontal and vertical directions. The test requires the rotary table to rotate for one cycle and the receiver to scan for 200 times.

  User manual added to DO-160G; New Class Q limits are added to protect VHF and GPS receivers, but not to conduct emission "HF notch" in class P; Change the test bandwidth from 100kHz to 1MHz. The previous version only used this bandwidth at 1GHz, but 960MHz used this value in DO-160G; Remove the 10kHz bandwidth option for test frequencies greater than 960MHz and replace it with high gain preplay.

  1.9 Transient sensitivity to Lightning induction in Chapter 22

  Various simulated lightning induction transient waveforms are injected into EUT connector pins, interconnecting cables and power lines by pins and cable bundles to determine whether the equipment will work as required during or after the test. When injected with a pin, the EUT is in the power-up working state. Check whether the EUT is normal after the test. Cable bundle injection simulates transient signals to the EUT interconnection cables and power cables through cable induction or ground induction. The EUT must be insulated from ground during testing. The signal applied to the EUT cable or wire is required to be carried on for at least 5 minutes at each polarity. Transient signals are click signals or combination signals (click signals, multi-hit signals, multi-pulse group combination), and EUT classification is performed according to pin injection, cable bundle injection, and test signal waveform.

  The user manual section has been added to DO-160G. Many comments and remarks in this chapter have been moved to the user manual. Remove the "resistance method" test that uses the pin injection test waveform to determine the source impedance; Add cable bundle test waveform 6, suitable for multi-pulse group test only; Modify pin injection calibration and test configuration diagram.

  1.10 Chapter 25 Electrostatic Discharge

  When air discharge is carried out, whether the EUT can work properly as required. This method is similar to GB 17626.2-2006, but this test requires EUT to be connected to the ground, and only air discharge is carried out. The test point is a place easily accessible to personnel, and 10 times of positive and negative 15kV air discharge are carried out on the test point.

  The test point is clarified in the DO-160G, specifically stating that the pin of the connector is not subject to this test.

  2 Conclusion

  RTCA/160 is equivalent to the European EUROCAE/ED-14 standard, which specifies electromagnetic compatibility requirements for airborne electronic equipment. In order to adapt to the development of airborne power system and electromagnetic compatibility test technology, people constantly modify the test grade, requirements and test methods. Meanwhile, SC135 will write a user guide for all sections before the next version of the DO-160 is released. The comparative analysis of DO-160G and DO-160F provides a reference for the design of airborne equipment test scheme.

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