EMC analysis of LF unstructured telecom networks

Transcription

1 COST 286: Joint Technical Action 2 EMC analysis of LF unstructured telecom networks, Heyno Garbe Institute for the Basics of Electrical Engineering and Measurement Science Leibniz Universität Hannover battermann@ieee.org 1

2 Content Idea for this joint technical action technical description of a PLC / BPL system effects of the data transmission The coupling path between the interference source and the victim will be depicted and analyzed. A new measurement method for the characterisation of the mains network (for the deduction of limits) will be presented. measurement results Summary. 2

3 Reasons for this Joint Technical Action (JTA) Unstructured data communication and telecom networks caused disturbances to other spectrum users. Powerline-communication (PLC) or broadband over powerline (BPL) is only a subset of these networks. Standardization process is going on for years now without a real agreement. Is it possible to find measurement techniques for a characterization of these networks? The results may be used in a set of applications! 3

4 Example: Inhouse-PLC - Schematic line (230 V) OFDM Technical data Modem Ethernet / PLC Ethernet TCP/IP protocol via the line Modem PLC / USB 84 carriers (OFDM) MHz Spectral power density 50 dbm/hz Special frequencies are notched (-30 db) 80 dbm/hz Home-Plug Power Alliance Standard 4

5 Effects? What is the effect of the PLC data transmission on the electromagnetic environment? Simple Test: In-house PLC modem connection (with 2 PCs connected) Short-Wave Receiver with an outdoor antenna Comparison of the measured antenna voltage with and without data transmission. => Determination of the influence on the signal to noise ratio (SNR) 5

6 Receiver with outdoor antenna - model PC 2 with PLC modem Yagi-Uda antenna PC 1 with PLC modem Mains with PLC signal y line with PLC Windom 6

7 Measurement: Influence of PLC outdoor antenna U / dbµv (Peak) Measured Feedpoint Voltage - Windom antenna without PLC with PLC notches Δ U / dbµv (Peak) Difference in Measured Feedpoint Voltage - Windom antenna notches 0 BC-TX f / Hz x 10 7 Voltage at the feed-point of the antenna f / Hz x Difference: with and without PLC 7

8 Noise impression of OFDM audio samples khz, AM Clear frequency BC, 6055 khz, AM High field-strength BC, khz, AM Medium field-strength Recorded with communication receiver (Icom IC-781) at the depicted outdoor antenna , 14:00 What about the use of an indoor antenna?... or a DRM receiver? 8

9 Influence on receiver with indoor antenna Δ U / dbµv Difference of the voltage of the rod antenna (with/without PLC) f / MHz Receiver chassis is connected to mains Difference of the voltage at the feedpoint of the antenna with/without PLC transmission in the same apartment with PLC transmission Worst case scenario. 9

10 Reasons for this joint technical action Disturbance by high rate data transmission Today used in Germany: NB30 BUT: field measurement in 3 m in the near field??? Conversion back to E-field (physically not reasonable) Low Reproduceability Alternative methods Longitudinal conversion loss (LCL) k-factor => Missing international agreement for limits 10

11 Mains used for telecommunication network Symmetry? Transitions? RJ-45 or USB to PC Load Fed with DM-Mode Modem Conversion to CM antenna mode current Mains Network Black Phase Blue Neutral Load Modem RJ-45 or USB to PC 11

12 Development of antenna mode current Radiation PLC modem power-line Partially converted to antenna mode current symmetrical feeding (Differential mode current) low symmetry changing impedances resonances (stubs) asymmetrical structure 12

13 Further Methodology Characterization of the disturbance scenario? Is it possible to describe the coupling between PLC application and receiver interference? broadband telecommunication service Short-wave Service (e.g. broadcast) Coupling Combination of line guided + field guided interference Transferfunction? 13

14 Coupling EMC model Generator with Feeding (source) Mains with sockets (channel) Radio with powersupply (victim) Generator with Feeding (source of noise) Mains network, including the sockets Radio with power supply (victim)??? 14

15 Disturbance scenario - CISPR The back-path for the common mode current is missing!???? Defined ground conditions reference ground? 15

16 Important for the measurement method? 1. Question What is the disturbance quantity? 2. Question What is the impact on the receiver? 3. Question How to deal with the undefined ground conditions? The noise source and the victim are coupled to ground! The coupling path has even a continuous coupling! 16

17 CM-current and resulting voltage I / dbµa Δ U / dbµv (Peak) Measured Common-mode current Difference in Measured Feedpoint Voltage (FD4) f / MHz o o The field strength is dominated by the commonmode current on the line the current is the reason for the radiation. (answer 1) Frequency dependent changes caused by mains characteristics are visible. windom antenna 17

18 Receiver with indoor antenna wanted field strength EW CMains/ANT CANT/RX Rodantenna with ant. factor AF Coupling network to mains Rod antenna Iasym,out Receiver CL,RX UW Receiver Mains wire Uir ICM,Ant ICM,Chassis Ground CRX/GND CANT/GND Coupling device 18

19 Characterization of the mains network The resulting antenna mode current on the mains is the disturbance quantity (answer 2) Proved by simulations and measurements The source and the victim must be defined (answer 3) Feeding and measurement of a symmetrical or asymmetrical current and measurement of the resulting antenna mode current at the chassis of the receiver Calculation of the coupling loss mains 19

20 Differential mode feeding DM in / CM out Both conductors 180 shifted 2 I in,sym L I out,asym Generator Common-mode choke Current-Balun Symmetry Voltage-Balun 5 nf 49 Ω 5 nf Current clamp Couplingnetwork Current clamp Feeding- Network PE N Mains RX-Chassis Receiver/ Radio-Dummy Measurement of the fed symmetrical current I sym,in and the asymmetrical current at the output I asym,out Coupling loss for differential mode feeding: C I sym,in = 20 log I asym,out L,M,sym 10 20

21 Common mode feeding CM in / CM out I in,asym I out,asym L PE N RX-Chassis Generator 5 nf 49 Ω Current clamp Mains Counterpoise Feedingnetwork 49 Ω 5 nf Current clamp Couplingnetwork Receiver Measurement of the fed asymmetrical current I asym,in and the asymmetrical current at the output I asym,out Coupling loss for common mode feeding: C I asym,in = 20 log I asym,out L,M,asym 10 21

22 Mains Coupling Loss - DM in / CM out C L,M,sym - with mains connection House new cabling House old cabling Empty house (no devices) C I sym,in = 20 log I asym,out L,M,sym 10 C L,M,sym / db blue green red house, new cabling house, old cabling empty house, no devices f / MHz This is no attenuation curve for DM-signal transmission! Solid line Median Dash dot Median t*std.dev. 22

23 Mains Coupling Loss - CM in / CM out C L,M,asym / db C L,M,asym - with mains connection House new cabling House old cabling Empty house (no devices) f / MHz C L,M,asym 10 blue green red I asym,in = 20 log I asym,out house, new cabling house, old cabling empty house, no devices Solid line Median Dash dot Median t*std.dev. 23

24 Feeding with comb-generator Generator Generator mains Counterpoise currentprobe CM-choke balun Common mode feeding Differential mode feeding 24

25 Characterization of the mains network Calculation of the Symmetrical decoupling factor based on the coupling loss mains n 1 C = ( C C ) db s L,M,sym,i L,M,asym,i n i = 1 Method for the rational derivation of limits for this kind of broadband telecommunication services (CISPR ) Based on the minimal SNR at the receiver the allowed input signal level (of the source) can be determined. 25

26 Coupling Rp = Uw Uir SNR CNetz/ANT E W Rodantenna AF Generator (Ui) Iasym,in Isym,in Mains CL,M,sym CL,M,asym Iasym,out Receiver CL,RX UW Uir ICM,Ant ICM,Gehäuse CTX/GND CNetz/GND CRX/GND CANT/GND ( ) 20log 50 ( ) I = E AF R + C + C in w P L,M L,RX 26

27 Influencing factors of CISPR Quantification of probability Derivation of limits just a value with a specified probability of a reception without disturbance. P R ( ; ) μr σr RP = α R actual signal-to-interference ratio, Rp Protection ratio 1. Simultaneous use of interference source and victim 2. Use of the same frequency 3. Use in a distance, that will allow disturbances 4. Full use of limits over large frequency ranges ( ) U = μ μ R + μ + μ μ + t σ t σ + σ + σ + σ + σ + σ Limit w m p z a c β u α w m u z a c 27

28 Summary Physical Problems Common mode current with radiation due to many asymmetries in the mains network The resulting common mode current on the mains is a valid quantity for the description of the disturbance. New technically based discussion of limits is needed CISPR (model for the calculation of limits) Measurement techniques for the characterization of the mains network have been presented The idea of the coupling loss mains (based on currents) and measurement results have been depicted. 28

29 Kiitos vastauksestasi + Kiitos kutsusta 29