Canards are not a 'RCS control problem' anymore than main wings and horizontal stabilizers. In fact, all leading and trailing edges on an aircraft reflect radar. The key is planform alignment.
Yes, they are. You are not going to get away with 'Chinese physics' here.
The rules for designing a radar low observable complex body are controls of:
- Quantity of radiators
- Array of radiators
- Modes of radiation
If there is a minimum necessary quantity of radiators on this complex body, the control of their arrays, or configurations and relationships, to each other comes into play. In this, everything is at least an 'issue of concern' if not outright a problem. If canards are necessary but their quantity ( 2 ) cannot be offset by the elimination of other major contributors, then they breached the line from being a normal 'issue of concern' to being a genuine problem.
The above is a drastic example but a necessary one.
Depending on a radiator A's location and array to other structures/radiators, the elimination of other structrures/radiators may not be sufficient to offset radiator A's contribution to final RCS. For the example above, we can work on shrouding the engines, cockpit treatment, etc., but as long as we cannot do anything to that array of radiators in the rear -- the vertical/horizontal stabs configuration that produces the dreaded 90 deg corner reflectors -- all our other works are essentially worthless. The rest of the aircraft can be below the graph but there will always be a large spike above, giving the aircraft away.
Same thing with the J-20's canards. You can bring on charts showing their -- alleged -- individual RCS measurement data like in post 4346, but for those who know better, those charts are meaningless in the absence of any data regarding rule 2: Control of array of radiators.
In other words, we need measurement data for the entire body in order to make any definitive judgement.
Further, complex bodies are unique in their final RCS values. Yes, these aircrafts have cockpits, pairs of wings and stabilators that are in same locations and configurations and they will produce a common RCS signature, but when there are additional radiators like antennas or panel gaps that are unique from aircraft to aircraft, the final RCS values are going to be as unique as the human fingerprints. That mean the canards' contributorship on one aircraft may not be as significant as on another.
If we are to take public opinions as approximate gauges, then the consensus among radar specialists is that the J-20's canards straddles the line between being an 'issue of concern' and being a genuine problem, and that is being generous in the absence of hard measurement data, which all know the Chinese government will not reveal.