Short Term Scientific Mission Scientific Report

Transcription

1 Short Term Scientific Mission Scientific Report Jacek Skrzypczynski, Institute of Telecommunications, Teleinformatics and Acoustics, Wroclaw University of Technology Wybrzeze Wyspianskiego 27 Pl Wroclaw, Poland May, 2006

2 Contents: Introduction Purpose of the visit Measurements Measurement set-up configuration First results of measurements Main results of measurements... 7 The results for 5 cm height of the wire... 7 The results for 80 cm height of the wire Additional measurements Conclusions Deliverables References

3 Introduction This is the report of the visit to the EMC Test Laboratory of ARC research GmbH,, Austria carried out as Short Term Scientific Mission of COST 286 Action. Section 1 explains the purpose of the visit. Section 2 presents the work that has been done and results of measurements. Finally, conclusions and perspectives are given in section Purpose of the visit Researches from Wroclaw University of Technology and from ARC research GmbH participate in works of COST 286 JTA1 [1]. Wroclaw group has modeled numerically aspects of GSM phone put in a vicinity of communication system cables. In September 2005 Jacek Skrzypczynski had completed Short Term Scientific Mission to the University of Split, FESB, Croatia. He had compared his simulation results with Split simulation results and then conducted measurements to validate numerical evaluations. The results of that STSM have been presented in a scientific report available to COST 286 action members and in publications accepted for Wroclaw EMC Symposium 2006 [2] and Barcelona EMC Europe 2006 Conference [3]. Split measurement set-up was organized in a laboratory room that was not screened, as presented in Fig.1. The antenna dipole was mounted on relatively big metal arm (it was a part of an antenna construction as seen in Fig.7.) and fed by a coaxial cable with no ferrite load. The main outcome of Split experiment was that quite a good coherence was achieved between simulation and measurements with exception for a few positions of the antenna, especially when dipole was placed near loaded end of the wire. Fig.1. Measurement set-up configurations: Split (top) and (bottom) 3

4 ARC research GmbH is in a possession of an anechoic chamber (Fig.1.) and is a producer of Precision Reference Dipole PRD of very compact construction. That gave an opportunity to perform measurements in more appropriate conditions then during Split experiment. Measurement set-up had been completed in the anechoic chamber and series of measurements had been conducted followed by comparison analysis of obtained results. 2. Measurements 2.1. Measurement set-up configuration Anechoic Chamber: Faraday cage with pyramidal foam absorbers type Emerson & Cuming VHP 26 and VHP 36 useable volume: length 6.6 m, width 3 m, height 3 m frequency range: up to 40 GHz Metal Ground Plane: size: 1.5 m x 4.3 m made of aluminium Wire: 1 m long 2 mm diameter height above ground plane: 5 cm and 80 cm made of brass Construction material for supporting the wire: Styrofoam dry wood Loading resistor position: reference point is 1.65 m from the edge of ground plane centre of the resistor is 17 mm above ground plane resistor itself is 5 mm long (without leads) Measurement Devices: The wire load resistor (100 Ohm at 900 MHz): as two SMA resistors mounted on a jig or as a leaded thin film resistor Measurement cables: Coax cables with altogether 13.3 db attenuation Signal Generator: Rohde&Schwarz SMT 03 (5 khz 3 GHz) with Level 13 dbm (equal to 1 V) EMI Test Receiver: Rohde&Schwarz ESIB 26 (20 Hz 26.5 GHz) with RBW 20 khz and VBW 1 khz 4

5 Dipole: Precision Reference Dipole PRD tuned for 900 MHz, 15.5 cm dipole length, balun attenuation 5.9 db, 20 dbm max. input power, dipole is connected with a signal generator via ferrite loaded cable, product of ARC research GmbH, Fig.2. Precision Reference Dipole PRD used as an antenna during STSM 2.2. First results of measurements In the beginning of experiment the wire load had been assembled as 2 SMA resistors mounted on a jig as can be seen in Fig.3. Fig.3. The wire load as 2 SMA resistors mounted on a jig Results presented in Fig.4. were acquired for 5 cm height of the wire above ground plane and for x and z positions of the dipole antenna. There is a difference between obtained results and results of simulation. We assumed that it was the result of printed circuit layout. The results were not satisfactory for us so we decided to assemble the wire load in a different way, which was more close to configuration taken for simulations. 5

6 jig jig Fig.4. Comparison of measurement results for a jig load with Split simulation results; Voltage across the 50 Ohm load versus the antenna position; Dipole parallel to X (top) and Z axes (bottom); Height 5 cm 6

7 2.3. Main results of measurements The results for 5 cm height of the wire In simulations loading resistor was placed vertically, close to the ground plate. So we had used a single leaded thin film resistor as shown in Fig.5. Fig.5. The wire load as a single leaded thin film resistor The results acquired for 5 cm height are presented and compared with Split simulations and Split measurements in Fig.6 and Fig.7. The results of measurement in this configuration are satisfactory for x and z positions of the dipole antenna, but less acceptable for y position what is in contrast to Split measurements that were the best fitting for y position. Split Fig.6. Comparison of measurement results for a single resistor load with Split measurement and simulation results; Voltage across the 50 Ohm load versus the antenna position; Dipole parallel to X axis; Height 5 cm 7

8 Split Split Fig.7. Comparison of measurement results for a single resistor load with Split measurement and simulation results; Voltage across the 50 Ohm load versus the antenna position; Dipole parallel to Y and Z axes (from top to bottom); Height 5 cm That outcome, a bit strange at first look, can be explained after comparison of pictures showing dipole and cable layout for all positions of the antenna (Fig.8. and Fig.9.). It can be seen that in experiment the cable is perpendicular to the dipole for x and z position. But for y position a part of the cable in close vicinity to the dipole is parallel to it. And that is probably the reason of lower amplitude of induced voltage. The situation was different in Split. Because of relatively large arm of the antenna, the cable was kept far away from the dipole in all three dipole positions. In y position the antenna arm 8

9 was perpendicular to the ground plane, while in x and y positions parallel to the ground. The antenna arm was made of steal and much bigger in size then the dipole itself. And that could be the reason of lower amplitude of induced voltage for x and y positions especially when that steal cylinder was close to the wire loaded end. I suppose that differences between results of measurements and simulations are produced by parasitic effects in measurement set-up. These effects were different in Split and so different consequences can be observed in experiment results. the dipole in x position the dipole in z position the dipole in y position the dipole in y position a part of the cable parallel to the dipole Fig.8. The dipole and cable layout for all 3 positions of the antenna in experiment the dipole in x position the dipole in y position Fig.9. The dipole x and y positions in Split experiment 9

10 The results for 80 cm height of the wire Measurements had been repeated for 80 cm height of the wire. The results are shown in Fig.10. and Fig.11. confronted with Split results. Split Split Fig.10. Comparison of measurement results for a single resistor load with Split measurement and simulation results; Voltage across the 50 Ohm load versus the antenna position; Dipole parallel to X and Y axes (from top to bottom); Height 80 cm 10

11 Split Fig.11. Comparison of measurement results for a single resistor load with Split measurement and simulation results; Voltage across the 50 Ohm load versus the antenna position; Dipole parallel to Z axis; Height 80 cm There are some differences between measured results. Most of them can be judged as relevant. Very astonishing is the fact that measurements results are higher then simulation results. We had been deliberating that aspect and came into conclusion that the key role was played by vertical part of the wire. The length of the wire vertical part was the only main difference between set-up for 5 cm and 80 cm height of the wire. So we decided to perform additional measurements in a set-up with no horizontal part of the wire Additional measurements First we had removed horizontal part of the wire and then performed measurements in a setup with only vertical part of the wire (about 80 cm long). Results are presented in Fig.12. and Fig.13. compared with simulation results for whole set-up and with results of earlier measurements. We can not perform detailed analysis of impact of vertical part of the wire on induced voltage without additional simulations and without information on voltage induced only in horizontal part of the wire and on a phase shift between both signals. But it is apparent that vertical part of the wire is of a great importance and any change in its configuration can influence results of measurements. 11

12 80 cm vert. 80 cm vert. Fig.12. measurement results for vertical part of the wire compared with earlier presented results; Voltage across the 50 Ohm load versus the antenna position; Dipole parallel to X and Y axes (from top to bottom); Height 80 cm 12

13 80 cm vert. Fig.13. measurement results for vertical part of the wire compared with earlier presented results; Voltage across the 50 Ohm load versus the antenna position; Dipole parallel to Z axis; Height 80 cm The last measurements to mention were done for 5 cm height of the wire and the load assembled as the jig with a metal screen as can be seen in Fig.14. It gives an approximation of voltage induced in only horizontal part of the wire (Fig.15. and Fig.16.) and should be the subject of further analysis. Fig.14. The wire load as screened 2 SMA resistors mounted on a jig 13

14 hor. hor. Fig.15. Comparison of measurement results for a jig load covered with a metal screen with Split simulation results; Voltage across the 50 Ohm load versus the antenna position; Dipole parallel to X and Y axes (from top to bottom); Height 5 cm 14

15 hor. Fig.16. Comparison of measurement results for a jig load covered with a metal screen with Split simulation results; Voltage across the 50 Ohm load versus the antenna position; Dipole parallel to Z axis; Height 5 cm 3. Conclusions It was found in Split experiment that configuration of a cable connection between the wire load and the receiver had influenced measurement results. In we have found that layout of the cable connecting the generator with the antenna have influenced measurement results. The load resistor assembled in different way gives different results as well. It is clear that antennas of different construction can change results of measurements too. It is understandable that change in any part of measurement set-up can change disposition of minimum and maximum induced voltage. Nevertheless the results accomplished by simulations and measurements are in quite a good agreement and can be judged as very good when it is recognised that the main objective of the generic problem is the evaluation of maximum voltage induced in the wire load. Lack of a good consistency can be observed only for a few positions of the antenna. The evaluated maximum value of induced voltage across the 150 Ohm termination is within limits of 15% - 25% of the input antenna voltage. Changes in the antenna polarisation and height of the wire have limited impact on maximum value of the wire load voltage. Deliverables There will be the following deliverables and publications: a scientific report available to COST 286 action members at least two publications on EMC International Conferences 15

16 References [1] [2] J. Skrzypczynski, V. Roje " Measurement Verification of Transmitting Antenna Modeling in the Vicinity of a Signaling Cable", Proceedings of 18th Wroclaw EMC Symposium, Wroclaw Poland, June 2006 [3] J. Skrzypczynski, V. Roje, S. Antonijevic, K. Staniec " Simulations and Measurements of Coupling Phenomena Between a Radiating Antenna and a Cable", Proc. of EMC Europe 2006 Conference, Barcelona, Spain, September