New concepts for EMC standards applicable to multimedia products

In the field of Electromagnetic Compatibility (EMC) two phenomena are considered: the emission and the immunity of electronic products. Emission measurements of products are performed to protect radio systems. We are talking about a conducted emission measurement when a current is measured and about a radiated emission measurement when a field quantity is measured. Immunity tests are performed to test the immunity of electronic products against the presence of electromagnetic disturbances. In the past decade, an evolution in electronic products has been observed. Firstly, electronic products include increasingly functionality. This is explicit for so-called multimedia products. Secondly, an increasing number of electronic products are equipped with radio-communication systems for, e.g., communication with a broadband network or communication with peripheral and associated equipment. New radio-communication systems typically operate at frequencies above 1 GHz and are positioned in the vicinity of other products at home. The receivers of the radio-communication systems, which are typically integrated into multimedia products, are sensitive. The expected proliferation of these ‘wireless multimedia products’ is enormous. For that reason, these new types of multimedia products include new potential disturbance sources as well as potential new victims. All the more when we realize that currently the EMC standards for multimedia products require radiated emission measurements and radiated immunity tests up to only 1 GHz. EMC standards are developed by various committees within the International Electrotechnical Commission (IEC). The International Special Committee on Radio Interference (CISPR) develops and maintains basic standards for conducted and radiated emission measurements. These basic standards are developed in CISPR subcommittee A (CISPR/A). Furthermore, CISPR includes subcommittees that develop so-called EMC product standards. For example, CISPR/I is responsible for the development of new EMC product standards for multimedia products, CISPR 32 for emission measurements and CISPR 35 for immunity tests. A few years ago, a new radiated emission measurement method for frequencies above 1 GHz has been developed and published in CISPR 16-2-3. This method is based on a Fully Anechoic Room (FAR). Maintenance of this method is still in progress. Moreover, the understanding of the electromagnetic behavior and uncertainty of measurement methods is an important topic within CISPR/A. For example, the question how receive antenna specifications relate to the uncertainty of the radiated emission measurement. Another example of a method for performing radiated emission measurements at frequencies above 1 GHz is the Reverberation Chamber (RC). This is a reflective chamber that physically operates as a resonant cavity from which the modes (standing wave patterns) are continuously varied by rotating one or more stirrer(s). A stirrer is an electrically conducting paddle wheel that varies the electromagnetic boundary conditions. The RC method is a statistical method that utilizes the multiple reflections inside a shielded enclosure, while the Semi Anechoic Room (SAR) method and the FAR method are deterministic methods and based on straightforward wave propagation. The content of this thesis include the results of three studies, which are related to the above-mentioned developments in EMC standards. The first study addresses the investigation of the deviation in radiated emission results caused by using different types of receive antennas. The receive antenna is used in radiated emission measurements to measure the emission emitted from the EUT. The receive antenna is characterized by a single number only, i.e., its Antenna Factor (AF). Conventionally, the assumption was that if the AF of receive antennas could be determined accurately, then the use of different receive antennas should yield the same radiated emission result. Earlier investigations already indicated that this assumption is questionable. The deviations due to the use of different receive antennas were investigated by comparing the results obtained by using commonly used receive antennas: tuned dipoles, bow-tie antennas, biconical antennas, log-periodical antennas, and double-ridged waveguide horn antennas. The deviations are investigated for the 3 m SAR facility. The deviations are investigated at frequencies below and above 1 GHz by using simulations. Two antennacalibration methods were taken into account, i.e., the free space method and the standardsite method. The tuned-dipole result was conventionally used as reference whereas the electric field-strength in absence of the receive antenna was recently introduced as the new reference. The reference obtained by a tuned dipole and the reference obtained by the electric field-strength in absence of the receive antenna were used to determine the deviations. This was performed to investigate the deviation values and their relation to the two references. In the operating bandwidths of the investigated antennas, a considerable ‘receive antenna type’ deviation is found of around 2 dB. The level of deviation due to the use of different types of receive antennas (2 to 3 dB) is defined as substantial in relation to the UCISPR value of 5 dB for 3 m SAR measurements. It was found that multilobing antenna-patterns caused higher deviations. Furthermore, it was found that the level of deviation due to the antenna type is not affected by the way the receive antennas were calibrated. Considering the uncertainties, we could conclude that the E-field reference as proposed in CISPR/A is neither an improvement nor a degradation compared with the tuned-dipole reference. At frequencies above 1 GHz, it was found that the beamwidth of the receive antenna is an important quantity related to the deviation. Approximately, a 60° beamwidth yields -1 dB deviation and a 30° beamwidth yields -4 dB deviation. The topic of conversion of emission results obtained from the RC method is mentioned in the second study. A standardized conversion method was applied to investigate the socalled conversion factors. These conversion factors are needed when results obtained from the RC method are translated to SAR/FAR results. The interesting feature of the applied conversion method is that the conversion factors are derived based on a reference quantity. The reference quantity is the important quantity for the protection of radio-communication systems. The conversion method is applied to investigate the conversion factors of the RC method towards the SAR method. From the derived conversion factors also the limit based on the SAR method can be translated towards the RC method. This is performed because the limit for the SAR method is successfully used already for many decades. We have numerically investigated the conversion factors of isotropic point sources, tuned dipoles, and a fixed-length dipole antenna. We have investigated the conversion factors experimentally by considering a CISPR 22 system-EUT configuration based on a TV, PC, and printer. The conversion factor for the RC method to derive a new limit based on the SAR method is approximately 4 dB. This means that the limit for the RC method is approximately 4 dB lower than for the SAR method. Moreover, the directivity of EUTs was investigated and the influence of the directivity effect on the conversion factors. A statistical model for EUT directivity was reviewed and based on this model a comparison of the directivity effect was performed for a fictitious EUT measured within either a RC or a FAR in the frequency range 1-6 GHz. From the statistical review, we could conclude that the directivity of the EUT plays not an important role in the conversion topic. However, from simulations of a fixed-length dipole of 1.5 m, it became clear that the directivity effect on the conversion factors depends on the polarization of the emissions. Horizontal polarization causes a higher deviation for the RC method while vertical polarization causes a higher deviation for the SAR/FAR method. This means that the polarization behavior of emissions of typical EUT configurations should be investigated in future in order to define proper conversion factors. In the third study, new concepts of immunity test-signals are investigated. EMC emission measurements or immunity tests are performed in order to cover certain interference scenarios. The conventional interference scenario for immunity tests was based on analog broadcast transmitters relatively far away from in-home electronic products. Mostly, the interference mechanism is nonlinear detection in the product, which accordingly could cause audio or video interference. Based on this interference scenario, the current 1 kHz 80% Amplitude Modulated (AM) signal is applied. We have defined a new interference scenario, i.e., the coexistence interference scenario. This interference scenario covers the existing situation of multimedia products with integrated radio-communication systems. Here, the disturbances sources are the radiocommunication signals that are typically digitally modulated signals. In addition, the disturbance sources are typically in the vicinity of victim products. The victims in the coexistence interference scenario are the sensitive receivers of the radio-communication systems. The receiver function of multimedia products with integrated radiocommunication systems is an important function that should be tested on immunity. Based on these two interference scenarios, the properties of Time Division Multiplexing (TDM) and Frequency Division Multiplexing (FDM) radio-communication signals were investigated. The following radio-communication signals were investigated: GSM signals, DCS signals, Bluetooth signals, wireless LAN (OFDM) signals, and UWB signals. The time behavior was investigated statistically by applying the Amplitude Probability Distribution (APD). The frequency domain properties were investigated by considering the spectrum. These investigations were supported by MatLab calculations. The time behavior of OFDM radio-communication signals was investigated. The properties of the radiocommunication signals were used to propose specifications for so-called Unified Disturbance Source (UDS) signals. A UDS is defined as an immunity test signal representative for a number of radiocommunication signals that has a interference potential equivalent to the actual radio communication signals. The study is completed by reviewing experimental evaluations of the UDS signal concepts for the use of coexistence immunity tests. It is an advantage that the UDS signals can be generated by using commonly available test equipment. In this way, representative coexistence immunity tests can be performed cost and time efficiently. Keywords: electromagnetic compatibility / electromagnetic interference / interference scenario / antenna factor / receive antenna / emission measurement / immunity test / coexistence immunity test / immunity test-signal / reverberation chamber / conversion of emission results / anechoic chamber / wireless communication / measurement uncertainty / EMC standards / multimedia.