November 4, 2024

Additional guidance on nerve stimulation compliance assessment using curve-fitting techniques 

Consultation closed December 6, 2024

 

Through this Notice, Innovation, Science and Economic Development Canada (ISED) clarifies its expectations regarding nerve stimulation compliance assessment where curve-fitting techniques are being used in accordance with section 5.3.1 of RSS-102.NS.MEAS or 7.1.1 of SPR-002. The content of this Notice is also intended to address the reporting deficiencies observed in certification applications reviewed by ISED.  

 

ISED will accept curve-fitting techniques, without the need to submit an enquiry, provided all the relevant information from the Notice 2024-DRS0004 and the details herein are included in the certification application.

 

Note that the guidance in this Notice serves to highlight the necessary information to support testing and compliance determination. All reporting requirements outlined in RSS-102.NS.MEAS must still be  included in the test report.  

 

Submissions utilizing curve-fitting techniques shall include the following information in the report: 

 

1. A detailed description of the Equipment Under Test (EUT) shall be provided. 

1. Information related to certification (i.e., ISED Certification Number, Applicant, HVIN , official product name, etc.) 
2. Technical information related to the EUT (i.e., operating frequency(ies), operational modes, modulation type, antenna type, hardware and software version, power supply and etc.) 

 

2. A detailed description of test equipment shall be provided. 

1. Information related to the client devices and power adapter used for testing, including the make, model and maximum charging power.
   1. The WPT client devices shall have a charging rate greater than or equal to the maximum charging rate of the WPT source.
   2. The power adapter shall provide the maximum voltage and current to the WPT source, ensuring the source transmits at maximum power.
2. Information related to the measurement equipment, including the manufacturer, software version, model number, calibration date and due date.  

 

3. A complete description of the coil(s) shall be provided. 

1. Information related to the coil(s), including geometry, number of turns, maximum RMS current and operating frequency(ies).  
2. Figure(s) clearly illustrating the location of the coil(s) within the EUT shall be provided, as shown in Figure 3 of the Notice 2024-DRS0004. 

 

4. The list of test configurations shall be provided. 

1. All test configurations shall be provided to demonstrate compliance in all applicable exposure conditions (i.e. maximum power charging mode, idle mode, direct exposure during device removal mode, etc.) and test positions (i.e. front, back, left, right, top and bottom).
   1. The EUT shall be tested at different battery status levels of the client, including by not limited to levels close to 0%, where charging rates are typically the highest. It shall also be tested at levels that are low, mid, and high.
   2. If only the declared worst-case test configuration is tested, clear justification based on measurement data demonstrating that other test configurations do not exceed the worst-case shall be provided.
    

   Note: ISED has generally considered justification using the maximum field strength (MFS) evaluation to determine the worst-case test configuration and/or test position acceptable.

2. The test frequency shall be listed for each test configuration.
3. When there are multiple coils and/or multiple charging frequencies, in addition to assessing the total transmission from all coils, all test configurations should be tested for each coil separately.

 

5. A summary of the exposure ratio results obtained for each assessment required as per RSS-102.NS.MEAS, including the worst-case NS-based exposure ratios (Total Exposure Ratios - TERs) shall be provided, as per section 5.5 of RSS-102.NS.MEAS. 

1. Spectrum plots across the entire frequency range from 3 kHz to 10 MHz shall be provided for each coil. The fundamental of each charging frequency must be active to ensure that all frequency components are included in the evaluation.
2. Any frequency components with emissions exceeding the probe sensitivity and within 20 dB of the fundamental (or maximum field strength level) shall be included in the assessment.

 

6. Time-domain plots shall be included to demonstrate the duty cycle for all test configurations. 

 

7. The MFS shall be provided following the methodology outlined in the Notice 2024-DRS0004.

1. The measurements grid to identify the MFS, including the description of the plane where the evaluation is being conducted (XY, XZ and YZ), shall be provided. Note that the spatial resolution will depend on the size of the EUT and the probe.
2. The MFS location shall be evaluated for both the magnetic (H) and electric (E)-fields.
3. A plot of the measured field strength in relation to the distance, as illustrated in Figure 4 of the Notice 2024-DRS0004, shall be provided.

 

8. Accurate measurements shall be provided based on the methodology outlined in the Notice 2024-DRS0004.   

1. As specified in the Notice 2024-DRS0004, the majority of the samples should be measured where 𝑑meas ≥ 1.7𝐷p is met. In many cases, measuring some samples closer than 1.7Dp may improve the model.
2. Accurate and uniform step sizes in all directions during measurements shall be ensured (ISED is aware that the illustrative example provided in Notice 2024-DRS0004 does not conform to this).
3. When performing measurements, the probe shall be normal (perpendicular) to the measurement plane and moving away from the source (e.g. the probe shall remain on the z-axis when measuring the x and y measurement plane). 

 

9. A complete analysis of the regression models shall be provided as per the Notice 2024-DRS0004.

1. ISED recommends using data analysis tools that perform regression analysis, such as the Data Analysis package included in MS Excel or similar software. It is the applicant’s responsibility to determine each parameter of the regression analysis should the end-user prefer to perform manual calculations.

 

10. A complete comparison table summarizing the analysis of the regression models, as shown in Table 2 of the Notice 2024-DRS0004, shall be included.

1. The 95% confidence intervals of the predicted lower and upper bounds for the selected regression model shall be provided.
2. The lower and upper bounds of the selected regression model shall be below the applicable limits. ISED notes that significant differences between the upper and lower bounds typically indicate that the model is not suitable for regression analysis.

NOTE: In general, ISED considers regression models with an adjusted R² greater than or equal to 0.99 as suitable.

  

11. A summary of field strength results shall include a clear statement of which model was chosen for the determination of compliance along with the maximum field strength results for both the E and H-field. 

 

12. Photographs displaying the full test set-up, particularly for the configurations yielding highest exposure, shall be provided, as per section 5.4.1 of RSS-102.NS.MEAS.

 

Comments related to this guidance may be submitted before December 6, 2024, at consultationradiostandards-consultationnormesradio@ised-isde.gc.ca.