4.3.2 Analysis of the Results in G3-PLC

Physical performance validation script results help to determine if a design is comparable with the Microchip reference designs. These tests allow detection of possible fails in the PLC reception or transmission paths associated with an incorrect PCB layout, incorrect component selection, etc.

Generally speaking, the most important result is the Frame Error Rate that represents the number of frames with errors received in the function of the attenuation (ATT) on the path or, more generally, depending on the received signal strength indication (RSSI).

The analysis of TX path results helps to determine:
  • Transmission Power: Depending on the RSSI value obtained in the results, we can evaluate if the board is transmitting the expected power. If the setup attenuation configuration is the same, the RSSI of the received frames from DUT will be similar to the results for the Microchip reference platform when the power supply source of the power amplifier is the same (12V by default).
    Figure 4-11. Typical RSSI Versus Attenuation on CEN_A with Microchip Reference EKs
  • On a clean environment setup, the TX path helps to analyze the transmission linearity of the DUT comparing the SNR_Payload, SNR Background or the LQI average for the same RSSI signal. Differences can be found mainly because of the transformer response on an isolated device but also there are no linear or ideal components, like coils, protection diodes or varistors, if no Microchip reference design BOM is selected.
  • On a similar calibration and transmission path, the TX_RMSCALC values must be similar as on Microchip reference boards. Otherwise it is highly recommended to calibrate transmission parameters using Physical TX Calibration.
The analysis of the RX path results helps to determine:
  • Sensitivity: Depending on the FER vs RSSI value obtained on the results, it can be determined if the background noise of the DUT is lower to the limit to pass G3-PLC certification.
    Important: The G3-PLC certification Sensitivity Performance Test defines a maximum of 5% FER at 60 dBuV of RSSI when running the ROBO Differential modulation.
    According to the Microchip experience, on a typical meter device connected to AC mains:
    Sensitivity (dBuV)RESULT
    <= 45VERY GOOD
    45 < TotalNoise <= 52GOOD
    52 < TotalNoise <= 58POOR
    >58POTENTIAL ISSUES
  • Impulsive Noise: Regarding Noised Symbols, it can be determined if there is impulsive noise on the reception. Additionally, comparing SNR Worst Symbol or SNR Impulsive with the SNR Payload, its influence can be determined. It causes errors in symbols so, a frame can be discarded depending on the impulsive intensity and the length of the frame increasing the frame error rate.
    Figure 4-12. Typical SNR Worst Symbol Versus RSSI on CEN_A Using DBPSK with Microchip Reference EKs
    Figure 4-13. Typical SNR Impulsive Versus RSSI on CEN_A Using DBPSK with Microchip Reference EKs
    Figure 4-14. Typical SNR Payload Versus RSSI on CEN_A Using DBPSK with Microchip Reference EKs
  • Narrowband Noise: Regarding Corrupted Carriers, it can be determined if there is narrowband noise on the reception. Additionally, comparing SNR Worst Carrier or SNR BE with the SNR Payload, its influence can be determined. This kind of noise is continuous and could be identified by accessing the SQLite database and analyzing the RX_SNR_CARRIER result values for each frame sent. It could be identified too on a clean environment when the G3-PLC Tone Map parameter does not correspond with the expected. It can be analyzed with tools like Noise Test.
    Figure 4-15. Typical SNR Worst Carrier Versus RSSI on CEN_A Using DBPSK with Microchip Reference EKs
    Figure 4-16. Typical SNR BE Versus RSSI on CEN_A Using DBPSK with Microchip Reference EKs
  • White Noise: If there is only white Gaussian noise during the test, the SNR payload, the SNR impulsive, the SNR be and the SNR background are similar. It is not critical in terms of the reception (because it applies to the complete bandwidth) when the sensitivity limits are not reached and is usually due to thermal noise, wrong PC or component selection.
    Figure 4-17. Typical SNR Background Versus RSSI on CEN_A Using DBPSK with Microchip Reference EKs
On a clean environment setup, the RX path helps to analyze the reception linearity of the DUT (mainly transformer response on an isolated device) comparing the LQI average for the same RSSI signal.
Figure 4-18. Typical LQI Versus RSSI on CEN_A Using DBPSK with Microchip Reference EKs
Detected errors on symbols or carriers is due to some impulsive or continuous carrier noise. The common sources for these noises are:
  • Continuous Narrow Band Noise: Usually associated with switching frequencies (or harmonics – mainly odd) of AC/DC and DC/DC converters. Follow Microchip PLC HW guidelines.
  • Impulsive Noise: Usually associated with other asynchronous transfers like SPI, I2C, radiated coupling,commonly related to a poor PCB Layout or BOM. Follow Microchip PLC HW guidelines.
  • Noise coming from mains.
According to the G3-PLC certification process, there are some limits that need to be accomplished, depending on the modulation and white background noise, regarding Frame Error Reception results with a maximum of 5% of errors:
Table 4-2. G3-PLC Performance SNR Limits Statements for White Noise
ModulationUnitCENELEC_ACENELEC_BARIBFCC
ROBO_DdB1121
DBPSKdB5555
DQPSKdB8888
D8PSKdB12121212
ROBO_CdB0000
BPSK_CdB3333
QPSK_CdB6666
8PSK_CdB10101010