In this installment in the series of blogs on UNECE Regulation 10, Revision 5, Amendment 1 (8 October 2016), hereafter referenced as R10.05, we will look at radiated emissions and immunity testing of Electrical/Electronic Sub-Assemblies (ESAs).
ESA RADIATED EMISSIONS (Annexes 7 and 8)
Like the vehicle radiated emissions testing annexes, R10.05 has separate requirements for broadband radiated emissions (Annex 7) and narrowband radiated emissions (Annex 8). The test set-up is the same for both measurements with only the measurement detectors and associated bandwidths, frequency step-sizes and dwell times differing between the tests. Unlike vehicle testing, the operating state(s) of the test sample is/are often the same for both measurements and so can be performed simultaneously, unless otherwise agreed with the Technical Service.
As with vehicle testing, broadband radiated emissions is a compulsory test, whereas narrowband radiated emissions is only necessary where the ESA contains one or more oscillators operating at frequencies above 9 kHz. Details of the differences between broadband and narrowband sources can be found in the previous blog in this series, and information on test exceptions can be found in the third blog in this series.
TEST FACILITIES
Annexes 7 and 8 specify that testing should be performed in an Anechoic Lined Shielded Enclosure (ALSE). An Open Area Test Site (OATS) can be used as an alternative measuring location. For details of the test sites and comparison of the benefits and drawbacks in each case please refer to the forthcoming White Paper that accompanies this series of blogs.
In both types of test facility, the ESA is placed on an insulated support 50 mm above a conductive ground plane, which is 900 mm above the floor of the test chamber. Power is fed to the ESA, and any necessary support equipment, via Line Impedance Stabilization Networks (LISNs) that provide defined stable reference impedance to help repeatability and offer some degree of filtering to protect the test power supply. The test harness is of fixed length between 1700 and 2000 mm, with 1500 mm laid parallel to, and 100 mm back from, the front edge of the ground plane.
The position of the ESA is normally determined by the connector to the harness, and is set back 200 mm from the front edge of the ground plane on a 50 mm insulated support. If the ESA is physically large, it may be necessary to extend the ground plane and perform the test in more than one position to ensure that all emissions are captured within the 3 dB beamwidth of the measurement antenna(s). ESAs that are of an irregular shape or that have unusual connection requirements e.g. connectors that must remain vertical will need to be discussed with the Technical Service to agree on an appropriate configuration for test. In situations like this where testing in strict accordance with R10.05 simply is not possible, it is important that the test set-up is documented thoroughly both in the worst-case record agreed prior to test and in the resulting test report.
The ESA is normally bonded to the ground plane using a low impedance cable (think short and flat). Where this isn’t possible, for example where the ESA is housed in a plastic case, then grounding of the ESA can be at the LISN on the power return line.
ANTENNA LOCATION & POLARIZATION
The phase centre of the antenna is located 1000 mm from the harness (i.e. 900 mm from the front edge of the ground plane). The antenna is aligned with the centre of the 1500 mm harness length that is parallel with the front edge of the ground plane at a height of 100 mm above it i.e. 1000 mm above the floor of the test chamber. The rationale for this is that radiated emissions below 1000 MHz are primarily from the wiring harness. At present testing is only required in the range 30 to 1000 MHz, however future revisions of R10 are likely to extend this range above 1000 MHz. Measurements above 1000 MHz are performed with the antenna re-located to align with the ESA.
Measurements are taken in both vertical and horizontal polarizations.
STATE(S) OF ESA DURING TEST
Before testing takes place, the state, or states, of operation of the ESA subject to test must be agreed with the Technical Service. ESAs that can operate with multiple input voltages are usually tested at the supply voltage that draws the most current from the supply, although there may be exceptions. If the ESA is particularly complex then the Technical Service may require testing in multiple modes in order to establish the ‘worst-case’. Further details on worst-casing can be found in the third blog in this series.
There is no requirement to test ESAs involved with “REESS charging mode coupled to the power grid” for narrowband emissions.
As with vehicle testing, ESAs that contain radio transmitters must be tested in transmit mode. Further details on this requirement can be found in the third blog in this series.
SUPPORT EQUIPMENT
The ESA should be operated with appropriate input and output signals and loading wherever possible to simulate ‘real-world’ conditions. Often such signals and loads are integrated into a load simulation box, or simply ‘load box’, that is placed on ad bonded to the ground plane at the LISN end of the harness. Where this is necessary, it is advisable to house the loads in a metal case with minimal apertures.
Data signals communicated over interfaces e.g. CAN, LIN, Ethernet etc. should be optically isolated to minimize any potential influence on the measurements.
Further details on support equipment are provided in the forthcoming White Paper that accompanies this series of blogs.
MEAUREMENTS & LIMITS
Measurements are taken with a scanning receiver or spectrum analyser, the measurement parameters of which are specified in Annex 7 (referenced in Annex 8).
Broadband limits are specified using a quasi-peak detector, however a peak detector measurement can be made with a 20 dB increase in the applicable limits, as for vehicle testing. Similarly, measurements that are on or above the limit must be measured on the corresponding frequencies with a quasi-peak detector for the final result.
Narrowband limits are specified using an average detector.
MEASUREMENT PROCEDURE
As there is a single antenna position (at present) and broadband and narrowband measurements can be taken simultaneously, only two measurement scans or sweeps are required for each antenna used (horizontal and vertical polarization) in each mode of operation.
The actual measurement procedure is the same as for vehicle testing. Modern receivers and spectrum analysers are usually controlled via software that automatically applies correction factors for the measurement system e.g. cables, antennas, attenuators etc. and logs the results. The end result is then a series of plots and/or tables identifying the maximum measured emissions overlaid with the applicable limits.
As with Annexes 4 and 5, measurements of ambient signals are required and must be at least 6 dB below the applicable limit. In the case of ESAs it may be necessary to perform multiple measurements in order to identify the source of any high level signals emanating from support equipment or the load box (if present).
ESA RADIATED IMMUNITY (Annex 9)
Unlike vehicle immunity testing, there are a number of alternative test methods specified for radiated immunity testing of ESAs: Anechoic Lined Shielded Enclosure (ALSE), Transverse Electromagnetic Mode (TEM) Cell, Bulk Current Injection (BCI) and Stripline. Any combination of methods can be used to cover the frequency range 20 to 2000 MHz. Which methods are most appropriate are dependant on the nature of the ESA and must be agreed prior to testing with the Technical Service.
Each of these alternative test methods would need a blog in itself so we will look at the ALSE and BCI methods here as they are the most common. For information on the TEM Cell and Stripline methods please see the forthcoming Whitepaper that accompanies this series of blogs.
TEST FACILITIES
The ALSE method uses exactly the same set-up as for radiated emissions testing. The key difference is the antennas used, as they need to be able to handle the power fed to them from the RF amplifier and signal generator used to generate the electromagnetic field.
Above 1000 MHz, the antenna is positioned to align with the equipment under test (EUT) to ensure that it is within the 3 dB beamwidth of the antenna. As with emissions testing, if the EUT is physically large then multiple antenna positions may be necessary for full illumination.
The BCI method uses a current clamp instead of an antenna. In this case, the probe is clamped around the test harness and power is fed into it at a pre-calibrated level. The BCI method is more efficient at lower frequencies than the ALSE method and consequently does not require as much power, and therefore a less powerful amplifier, to achieve the required test level.
BCI PROBE LOCATION
The set-up for BCI testing is different than for ALSE testing and therefore requires some adjustment to the layout on the ground plane. The key differences are that the harness should be 1 m long, and that it should be laid in a straight line from the LISNs to the EUT. Three probe positions are mandated at 150 mm, 450 mm and 750 mm from the EUT connector. The length of the harness and applicable probe positions can be agreed with the Technical Service prior to test to reduce the amount of testing, where technically justified.
TEST LEVEL & MODULATION
The test level is set in R10.05 at 30 V/m rms in over 90% of the range 20 to 2000 MHz, with a minimum of 25 V/m rms throughout the range for ALSE tests. For BCI, the injection level is specified at 60 mA.
Approval Authorities may require that testing is performed at higher test levels in order to provide additional confidence in the performance and allow for any minor production variations, however this is for the manufacturer to agree with the Technical Service prior to test.
The applied field is amplitude modulated (AM) in the range 20 to 800 MHz, to a depth of 80% at 1 kHz to simulate the type of narrowband signals that may impinge on the vehicle from external sources.
In the remainder of the frequency range, 800 to 2000 MHz, the applied signal is pulse modulated (PM) with a TON of 577 µs and period of 4,600 µs, to simulate the type of narrowband pulsed signals typical of GSM cellular communications.
RF is normally injected onto the harness from each connector in turn, however complex and inter-linked harnesses need careful consideration to avoid over testing.
It is advisable to perform BCI tests in some form of shielded enclosure or Faraday cage to prevent disturbance of nearby electronic systems and radio receivers.
STATE(S) OF ESA DURING TEST
The operating mode, or modes, to be tested are agreed with the Technical Service prior to test and are based on the immunity related function(s) of the EUT. See the third blog in this series for information on immunity related functions.
ESA MOMITORING and PERFORMANCE CRITERIA
In order to determine if the EUT is adversely affected by electromagnetic fields, it is necessary to monitor the performance during testing. For a simple EUT this could be as straightforward as monitoring indicators with a camera. For complex EUTs the amount of monitoring required could be significant; all of which must be filtered or optically isolated to prevent RF coupling outside of the chamber. This may involve using one or more laptops to monitor communication busses, custom monitoring/simulation consoles, pneumatic fingers operated by compressed air to operate switches and so on. The practicalities of performing a test in a chamber should not be underestimated and preparation is essential to save time and money at the time of test.
Radio links may need to be established and maintained during testing e.g. Bluetooth, GSM, GPS. This can also prove challenging and may require preparation of feed-through panels in the chamber wall and mounting of suitable external antennas on a mast to ensure consistent reception.
R10.05 is only concerned with immunity related functions, so “failures” of the equipment during test do not necessarily mean that the EUT fails Type Approval. Where signals are monitored during test then it is a good idea to agree an acceptable tolerance with the Technical Service prior to test to avoid confusion and prevent delays in production of the Test Report that will ultimately be attached to the Type Approval Certificate.
In the next instalment in this series of blogs we will look at transient emissions and immunity testing of ESAs in accordance with Annex 10 of R10.05.
REFERENCES
- UNECE Regulation 10, Revision 5 (9 October 2014):
- https://www.unece.org/fileadmin/DAM/trans/main/wp29/wp29regs/2015/R010r5e.pdf
- UNECE Regulation 10, Revision 5, Amendment 1 (8 October 2016):
- CISPR 25: 2002 + Corrigendum: 2004 – Radio disturbance characteristics for the protection of receivers used on board vehicles, boats, and on devices – Limits and methods of measurement
- Please note that this standard has been withdrawn, but is available for download free of charge:
- https://webstore.iec.ch/publication/12216
- ISO 11452-1 Third Edition 2005 + Amendment 1: 2008 – Road vehicles – Component test methods for electrical disturbances from narrowband radiated electromagnetic energy – Part 1: General principles and terminology
- Please note that this standard has been superseded and that ISO standards are not available free of charge.
- https://www.iso.org/standard/38001.html
- https://www.iso.org/standard/45933.html
- ISO 11452-2 Second Edition 2004 – Road vehicles – Component test methods for electrical disturbances from narrowband radiated electromagnetic energy – Part 2: Absorber-lined shielded enclosure
- ISO 11452-3 Third Edition 2001 – Road vehicles – Component test methods for electrical disturbances from narrowband radiated electromagnetic energy – Part 3: Transverse electromagnetic mode (TEM) cell
- Please note that this standard has been superseded and that ISO standards are not available free of charge.
- https://www.iso.org/standard/24569.html
- ISO 11452-4 Third Edition 2005 + Corrigendum 1: 2008 – Road vehicles – Component test methods for electrical disturbances from narrowband radiated electromagnetic energy – Part 4: Bulk current injection (BCI)
- Please note that this standard has been superseded and that ISO standards are not available free of charge.
- https://www.iso.org/standard/37414.html
- https://www.iso.org/standard/54749.html
- ISO 11452-5 Second Edition 2002 – Road vehicles – Component test methods for electrical disturbances from narrowband radiated electromagnetic energy – Part 5: Stripline
