ABSTRACT
Multiple-input multiple-output (MIMO) technology enhances the performance of PLC systems by utilising multiple ports for sending and receiving signals (see Chapters 8, 9, 12, 14 and 24). Beamforming or precoding is used in several current power line communication (PLC) systems (see Chapters 12 and 14) and significantly improves their performance as seen in Chapters 8 and 9. The influence of MIMO transmission on electromagnetic interference (EMI) is addressed in Chapter 7. In particular, the influence on EMI, when feeding signals on transmit ports other than the traditional differential feeding between L and N, is compared and analysed. However, Chapter 7 does not touch on the effects on EMI in detail, when using a particular MIMO scheme at the transmitter and simultaneous transmission on several ports. A comparison of MIMO schemes for PLC can be found in Chapter 8. This chapter discusses how precoding or beamforming influences EMI. The analysis, in this chapter, is based on the MIMO EMI measurements performed at the ETSI STF410 measurement campaign (see Chapters 5, 7 and [1–3]). Section 16.2 briefly recalls the EMI measurement setup. Section 16.3 provides a theoretical analysis of expected EMI for different beamforming modes based on the correlation of transmit signals. Next, a detailed statistical analysis of EMI for different beamforming modes is given in Section 16.4. A point of interest is whether appropriate precoding can mitigate EMI effects. This question opens the second part of this chapter where ideas and first results of an EMI-friendly beamforming are presented (see Section 16.5). Section 16.6 addresses the issue of how PLC modems can obtain information about EMI properties of the PLC network.
