I don't know if anyone posted it already, though I like to share this regarding the pro and cons of the canard design on RCS.
There is a research paper addressing the issue in a Chinese publication titled "Radar cross-section effect of canard"
You can download the pdf file at
Basically what they did is use the more accurate MLFMM (multi level fast multipole method) to simulate instead of the Physical Optics simulation algorithm used in "A Preliminary Assessment of Specular Radar Cross Section Performance in the Chengdu J-20 Prototype" by Dr. Carlo Kopp.
After that, they built a canard model to run the RCS test in the anechoic chamber.
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Key takeaway in the paper for canard vs. conventional configuration.
1. Neglectable frontal RCS increase compare to conventional under cruising conditions within +-5° deflection after mitigation.
2. Side RCS is lower than conventional due to no secondary reflection between vertical stabilizer and horizontal stabilizer.
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Ways to mitigate
1. Apply RAM to the gap between the fuselage and canard
2. Chamfer the rear edge of the canard to reduce scatter
3. Trailing edge parallel to the main wing on the other side
4. Use appropriate structure and RAM material on the trailing edge
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I think this picture shows exactly what those mitigate methods on the J-20
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