4.3.4 Analysis of the Results in PRIME
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).
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 4-23. Typical RSSI Versus Attenuation on CHANNEL 5 with Microchip Reference EKs 
- On a clean environment setup, the TX path helps to analyze the transmission linearity of the DUT comparing the CINR and EVM 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 RMSCALC values must be similar as on Microchip reference boards.
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 PRIME certification.Important: The PRIME certification Sensitivity Performance Test defines a maximum of 0.2% FER on an asymmetric Side-by-Side setup scenario (CENELEC CISPR16-1 LISN in one side and PRIME Adaptation LISN on the other side) without attenuation for interchanges of 2000 frames with a specific format.According to the Microchip experience, on a typical meter device connected to AC mains and using R_DBPSK modulation:
Sensitivity (dBuV) RESULT <= 45 VERY GOOD 45 < TotalNoise <= 52 GOOD 52 < TotalNoise <= 58 POOR >58 POTENTIAL ISSUES - Impulsive Noise: 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. Not robust modulations
can not help to decode properly frames with impulsive noise because interleaver
only works in the frequency domain (carriers), not in the time domain (symbols).
The impulsive noise on the reception can be determined:
- Regarding the percentage of impulsive noised symbols.
- On robust modulations, detecting a BER Soft Maximum far of the BER Soft Average. In not robust modulations BER Soft Max is equal to BER Soft.
- Detecting an EVM Payload maximum far of the EVM Payload average.
- It can be analyzed with tests like Noise Test.
- Narrowband Noise: Regarding the percentage of corrupted carriers, it can be determined if there is narrowband noise on the reception. It is detected internally comparing the SNR for each carrier and symbol. This kind of noise is continuous and can be analyzed with tests like Noise Test.
- Continuous Narrow Band Noise: Usually associated with switching frequencies (or harmonics – mainly odd) of AC/DC and DC/DC converters.
- Impulsive Noise: Usually associated with other asynchronous transfers like SPI, I2C, radiated coupling,commonly related to a poor PCB Layout or BOM.
- Noise coming from mains.
- Thermal noise.
On a clean environment setup, the RX path helps to analyze the reception linearity of the DUT (on an isolated device, the distorsion comes mainly by the transformer response or saturation) comparing the CINR average for the same RSSI signal respecting the Microchip reference. It should be higher than 17dBs for 8PSK according to the PRIME Test Book.
