Company report to support the development of the Ecma MM-EMF technical report (attached)

Transcription

1 Ecma/TC20/2009/019 DATE CIRCULATION: FROM: TO: DOC TYPE: TITLE: AUTHOR: P.A. Beeckman, Philips Applied Technologies Members Ecma TC20-MM-EMF Company report to support the development of the Ecma MM-EMF technical report (attached) Total Radiated Power Measurement Results of Multimedia products in Reverberation Chamber; Unintentional radiators K. Banerjee VERSION:, DOC ID: SUMMARY: The worst-case Total Radiated Power (TRP) of a number of multimedia products without intentional radiators has been measured in a reverberation chamber (RvC) in the radiated frequency range from 80 MHz up to 6 GHz. The RvC-measurement method is a straightforward method for quick assessment of the EMF properties of products in the radiated frequency range. From the measurement results, it can be concluded that typical multimedia products (unintentional radiators) radiate much less (in the mentioned frequency range) than the lowpower exclusion limit of 20 mw that can be applied to demonstrate compliance of multimedia products against the electromagnetic field exposure requirements. Ecma International Rue du Rhône 114 CH-1204 Geneva T/F: /01 For Ecma use only

2 Report EMC Center Philips Applied Technologies To Members Ecma-TC20-EMF-MM Author: K. Banerjee HTC Tel: Ref: Date: Total Radiated Power Measurement Results of Multimedia products in Reverberation Chamber; Unintentional radiators Version: Date: Filename: TRP unintentional radiators Classification: Page 1 of 10

3 Contents List of abbreviations 3 1 Introduction Background Approach 4 2 Total Radiated Power Measurements Test set-up and procedure List of equipment Determination of maximum chamber loss factor (ACF max ) Measurement results Pictures of test set-up 9 3 Conclusion 10 4 References 10 Page 2 of 10

4 List of abbreviations CL EMF EUT ECMA MM RvC SAR TRP Consumer Lifestyle Electromagnetic Fields Equipment Under Test European Computer Manufacturer Association Multimedia Reverberation Chamber Specific Absorption Rate Total Radiated Power Page 3 of 10

5 1 Introduction 1.1 Background Consumer lifestyle (CL) products have to comply with requirements for exposure to electromagnetic fields (EMF). Since no product specific EMF standard exists for CL products, the generic EMF standard EN62311 [1] may be applied for compliance measurements. No technical details on EMF compliance tests are however described in [1]; this has given rise to a need to develop a low-effort product specific standard for CL products, which is currently being carried out under the umbrella of ECMA [2]. In [3] a detailed description is given on three issues concerning the current method of testing. It has been proposed to apply the concept of total radiated power (TRP) measurements to CL products as a method to determine its EMF compliance. It is stated that: If the average power emitted by an apparatus operating in the frequency range 10 MHz 300 GHz is less than or equal to 20 mw, then the apparatus is deemed to comply with the basic restrictions without further testing. The Reverberation Chamber (RvC) has been put forward to be used in the TRP measurement method. Based on the descriptions given in [3] the test method and test set-up for TRP measurements have been further developed. In [4] and [5] a detailed description is given on the test set-up, the RvC calibration method and the TRP measurement method. Additionally, automated software programs have been developed in the frequency ranges MHz and 1 6 GHz for the determination of the TRP. TRP measurements are carried out in two ranges, namely MHz and 1 6 GHz. The obtained values represent the worst case estimate of the TRP of that range, since these values are corrected for the maximum chamber loss factor in that range. Further details are given in 2.3. The TRP values measured in the two ranges should be added to determine the worst case TRP in the overall frequency range of 80 MHz up to 6 GHz. 1.2 Approach A number of TRP measurements have been carried out using the method as described in [4]. Measurements were carried out on a range of multimedia (MM) products classified as unintentional radiators, i.e. products which do not contain an to intentionally transmit RF power. The obtained results were analysed and compared to the TRP-limit of 20 mw. Page 4 of 10

6 2 Total Radiated Power Measurements 2.1 Test set-up and procedure The block diagram of the TRP measurement set-up is given in figure 1. Reverberation Chamber Horizontal stirrer Horn Vertical stirrer or LogPer LF/HF band-pass filter RMS power sensor Preamplifier Power meter EUT Figure 1 TRP test set-up in RvC Power measurements are carried out over a period of 6 minutes in continuous stirred mode over two frequency ranges: MHz (band 1) and 1 6 GHz (band 2). The measured values of power are corrected for the extra (pre-) amplification and the loss introduced by the LF/HF band pass filter. This value is then corrected for the maximum chamber loss factor for the average power over each band. Further details on the chamber loss factor can be found in [4] and in List of equipment Control PC The following table gives the list of equipment, type numbers/id s and associated frequency ranges. Table 1 Equipment list No. Description Type/id Frequency range 1. Reverberation Chamber ETS Lindgren (MSC14) 80 MHz 18 GHz 2. LogPeriodic ETS Lindgren 30 MHz 2 GHz 3. Horn EMCO GHz 4. LF Band Pass Filter Mini circuits 100 MHz 1 GHz SHP 100+ and SLP HF Band Pass Filter Mini circuits 1 6 GHz SHP and VLF Pre-amplifier Miteq CE MHz 26 GHz 7. Power sensor R&S NRV-Z2 10 MHz 18 GHz 8. Power meter R&S URV5 9 khz 18 GHz Page 5 of 10

7 2.3 Determination of maximum chamber loss factor (ACF max ) Before TRP measurements can be carried out on actual EUTs, a Reverberation Chamber calibration has to be performed to determine the losses which are inherently associated with the chamber. Calibration is carried out according to [6]. A short description of the process is given in this paragraph. The block diagram of the calibration set-up is shown in figure 2. Reverberation Chamber Horizontal stirrer Vertical stirrer 3 Transmit Horn or Transmit LogPer Receive Horn or Receive LogPer 2 1 Dual directional coupler Spectrum analyser Signal generator Power sensors Power meter Control PC Figure 2 Calibration test set-up in RvC The forward and reverse power per frequency point is measured by the power meter. From these values, the net power is calculated and recorded. Similarly, the received power (P received ) is measured and recorded by the spectrum analyser for each frequency point. The stirrers are rotated continuously for 6 minutes per frequency point. During these 6 minutes, approximately 90 individual measurements are recorded for P input and P received. The average input power and receive power is calculated from these values; P input avg and P received avg. Page 6 of 10

8 The chamber loss factor called as the Antenna Calibration Factor (ACF) is calculated (per frequency point) using the following formula; Figure 3 and figure 4 show the ACF values in the frequency range MHz and 1-6 GHz respectively. ACF max ACF max Figure 3 ACF MHz Figure 4 ACF 1 6 GHz Figure 3 and 4 also show the maximum value of the ACF per frequency range. Table 2 Maximum value of ACF per frequency range Frequency range ACFmax MHz db 1 6 GHz db For broadband TRP measurements, the ACF max is used as the correction factor, meaning that a worst case estimate of the TRP is obtained. Page 7 of 10

9 2.4 Measurement results Measurements were carried out on a range of TV sets and monitors. The mode of operation was chosen according to the mode in which EMC measurements were carried out. Primarily a background measurement was done in an empty chamber (see measurement result in first row of table 3) to determine the noise floor. For all EUTs, measurements were carried out in two ranges ( MHz and 1 6 GHz) in stirred mode over a period of 6 minutes. From the results given in table 3, it can be seen that the TRP levels of typical CL product (unintentional radiators) lie far below the low-power limit of 20 mw. No. EUT TRP in µw MHz Table 3 Worst-case TRP measurement results TRP in µw 1 6 GHz Total TRP in µw 80 MHz 6 GHz Remarks 1. Background Empty RvC 2. 19PFL3404H 19 inch TV set 3. 19PFL3404D/xx 19 inch TV set 4. 22PFL3404H/xx 22 inch TV set 5. 22PFL3404/xx 22 inch TV set 6. 22PFL3404D/xx 22 inch TV set 7. 26PFL3404H/xx 26 inch TV set 8. 32PFL5604H/xx 32 inch TV set 9. 42PFL5604H* 42 inch TV set PFL5604H* 42 inch monitor inch 3D monitor In CISPR 13 set-up In CISPR 13 set-up In CISPR 13 set-up In CISPR 13 set-up In CISPR 13 set-up In CISPR 13 set-up In CISPR 13 set-up In CISPR 13 set-up In CISPR 22 set-up Connected to PC, keyboard, mouse Scrolling H pattern In CISPR 22 set-up Connected to PC, keyboard, mouse 3D pattern *The 42 inch TV set/monitor (42PFL5604H) was measured once using the CISPR13 set-up (i.e. as TV set with colour bar - measurement 9) and once using the CISPR 22 set-up (i.e. as monitor, with test PC and scrolling H pattern - measurement 10). TRP values measured in CISPR 22 set-up are slightly higher. This may be because of the presence of additional equipment (PC, keyboard, mouse) and cables inside the chamber. See 2.5 for pictures. Page 8 of 10

10 The worst-case TRP in the frequency range of 80 MHz up to 6 GHz ranges from approximately 10 µw to 200 µw (which is equivalent to -20 dbm up to -7 dbm). Compared to the low-power limit of 20 mw (13 dbm), the worst-case TRP of these MM-products is more than 20 db (factor 100) lower. It should be noted from the results in Table 3 that in general the higher frequency range (1 6 GHz) shows a larger worst-case TRP value than the worst-case TRP values of the lower frequency range. This is partially due to the fact that the upper frequency range is approximately 6 times larger than the lower frequency range. Furthermore, it is likely that the spectral content in the upper frequency range does not extend to 6 GHz, and therefore the calculation of the worst-case TRP is overly conservative by applying the maximum ACF value in this range (see Figure 4). 2.5 Pictures of test set-up The following photographs give details of the setup of some EUTs and measuring equipment inside the RvC. LogPer used in MHz range along with LF band pass filter and pre-amplifier Horn used in 1-6 GHz range along with HF band pass filter and pre-amplifier 32 inch TV set from front in CISPR 13 set-up 32 inch TV set from rear in CISPR 13 set-up 19 inch TV set on foam tables inside RvC. Horizontal stirrer and receive position visible 3D monitor connected with PC, keyboard and mouse. 3D pattern generated on screen. 42 inch TV set in CISPR 22 set-up. Connected to PC, keyboard and mouse. Scrolling H pattern generated on screen 42 inch TV set in CISPR 22 set-up. Meandering of connected cables at the rear visible. Receive position visible. Page 9 of 10

11 3 Conclusion The developed method [3][4] of determining the worst-case TRP of products in an RvC is a straight-forward method for quick assessment of the EMF properties of products in the radiated frequency range (> 80 MHz). From the measurement results given in table 3, it can be concluded that typical MM products (unintentional radiators) radiate much less than the lowpower TRP limit of 20 mw. In order to have an understanding on the entire scope of multimedia products, as a next step, similar measurements will be carried out on products having multiple intentional radiators. 4 References [1] IEC International Standard Assessment of electronic and electrical equipment related to human exposure restrictions for electromagnetic fields (0 Hz 300 GHz). [2] ECMA International Technical Report ECMA TC Guide for assessment of human exposure to electromagnetic fields from multimedia products in accordance with IEC/EN [3] Feasibility study to apply total radiated power measurements for EMF assessments. EMC center memorandum EMC-08-PAB-006-MEM, Pierre Beeckman, dated [4] Continuation of a feasibility study to apply total radiated power measurements for EMF assessments. EMC center memorandum EMC-08-JVDM-007-MEM, Jaco van der Merwe, dated [5] Reverberation Chamber Calibration Process for EMF TRP measurements EMC center memorandum EMC-09-KB-MEM, Konika Banerjee, dated [6] IEC International standard Testing and measurement techniques Reverberation Chamber test methods Page 10 of 10