How to test the signal integrity of J1939 cable

How to test the signal integrity of J1939 cable

Testing the signal integrity of J1939 cables can start with eye diagram analysis, error frame monitoring, impedance matching testing, attenuation and noise suppression testing, etc. The following are specific instructions:

Eye diagram analysis: Use an oscilloscope to collect the eye diagram of the differential signal between CAN_S and CAN_L. Eye diagram can intuitively reflect the amplitude, timing, and noise situation of a signal, and is an important tool for evaluating signal integrity.

Error frame monitoring: Build a J1939 test network and use tools to monitor bus error frame rates. A high frame rate error may indicate poor signal quality or interference.

Impedance matching test: J1939 standard requires a terminal resistance of 120 Ω, and the characteristic impedance of the cable needs to be matched with it. The impedance curve of the cable can be measured using a Time Domain Reflectometer (TDR) to ensure its stability within a certain range across the entire frequency band, avoiding signal reflection caused by impedance discontinuity.

Attenuation and noise suppression test: tested using a network analyzer. Simultaneously detect common mode/differential mode noise through a spectrum analyzer.