Sir Gambit thank you for the detailed info, but can you please go over how the Europeans have been able to reduce the RCS of EuroFighter and Rafale whom have canards.
The word 'reduce' is somewhat ambiguous. Do you mean a reduction from an existing planform? Like what Boeing did with the F-15SE and the redesigned F-18? Or do you mean to create a planform from start with a specific RCS value in mind?
With the F-15SE, Boeing converted conformal fuel tanks to become weapons bay. Basically we covered up all the weapons related doo-dads that added to the the aircraft's base RCS figure to create the final RCS figure. Then we slightly angled the twin vertical stabs to eliminate those huge corner reflectors. Those modifications cannot be made unless a detailed study of the aircraft's current aerodynamics reveal there would be no adverse effects.
Then we can introduce material modifications like this example...
Reduction of the RCS of the leading edge of a conducting wing-shaped structure b
The radar cross section of the leading edge of a conducting wing-shaped structure is reduced by replacing part of the structure with a lossless dielectric material. The structure retains its original external shape, thereby ensuring that the aerodynamic properties are not altered by the structural changes needed to reduce the radar cross section.
The leading edges of flight control surfaces are, for the frontal aspect, the highest contributors of the RCS figure. Installing RAM will reduce the amount of energy that can be reflected off these leading edges. But RAM introduce its own complications such as thickness and bandwidths and is a different topic for now.
Active or passive -- canards
ARE flight control surfaces and their locations make them the firsts of the flight control surfaces to contribute to the final RCS figure. An aircraft has the standard configuration of paired wings, horizonal stabs and a single vertical stab for five leading edges. Not counting intake leading edges or various communication antennas. Now add a pair of canards and you have seven. An inevitable increase in RCS. May be the design require canards, may be not.
On the other hand, the F-117's planform began in the opposite direction, that Lockheed effectively set down an RCS figure, or goal, and the design team must shape the aircraft in anyway to meet that figure.
F-117A: The XST
Irv Waaland, a Northrop designer knew that Northrop had a problem. Northrop's analysts had concluded that it was most important to reduce its vehicle's RCS from the nose and tail and the nose-on RCS-the view an adversary had in the critical head-on engagment-was more important than the rear aspect. It's XST design was a diamond with more sweep on the leading edges than the trailing edges. From the rear, it had low RCS as long as the radar was no more than 35 degrees off the tail.
But the DARPA requirement treated RCS by quadrants: The rear quadrant extended to 45 degrees on either side of the tail, thereby including the parts of the airframe where the Northrop design's RCS spiked. Waaland could not solve the problem by increasing the sweep angle of the trailing edges, the aircraft would become uncontrollable.
So now we have Lockheed and DARPA essentially treat the RCS figure as the dominant factor for the design. If Lockheed at that time could not meet that RCS figure requirement and even if the final design proved to be flight capable, there would be no 'stealth' aircraft at all. Up until the F-117, aircraft designs have always placed aerodynamics as dominant factor. The quote above had Northrop but the requirement was applicable to all competitors.
Could the F-117 have canards? Yes, and they would have the same radical sweep angle as the rest of the other flight control surfaces on the final F-117 planform. But Lockheed decided to eliminate a contributor to the aircraft's total RCS -- the canards -- and have the aircraft use a higher than average take-off/landing speed instead.
F-117A Nighthawk Stealth Fighter Attack Aircraft - Air Force Technology
The elevons do not act as flaps to reduce the rate of descent for touchdown, so the landing speed of the F-117A is high, at about 180mph to 190mph, and a drag parachute is used.
The F-16's landing speed is about 20-30mph less, for example.
The F-117's sharper sweep angle for all flight control surfaces was for RCS, not aerodynamics, purposes. Lockheed succeeded where Northrop failed, but you must understand that Northrop did not failed by much. For all we know, Northrop may have missed the required RCS figure by a razor thin margin and their design may have carried more weapons than Lockheed's design. If Lockheed decided that the higher than average take-off/landing speed was unacceptable and installed canards or reduce the wing sweep angle, we may be looking at Northrop's F-117 instead of Lockheed's.
The Eurofighter's and the Rafale's lower than average RCS was from paper inception, not from modifications of a current flying design. As such, the designers were able to offset the canards' contribution to the total RCS by partially recessing externally mounted weapons and having sharper than average wing sweep angle...
Eurofighter Typhoon - Wikipedia, the free encyclopedia
Many important potential radar targets, such as the wing, canard and fin leading edges, are highly swept, so will reflect radar energy well away from the front sector.
I am not going to discuss the Rafale's Thales Spectra system as that is not part of the base airframe and planform of the aircraft. The Spectra can be turned off or removed whereas flight control surfaces are structural requirements.
Canards offer much positives in terms of flight controls and maneuverability and we have studied them using the F-15.
F-15 S/MTD - Wikipedia, the free encyclopedia
Combined Canard, Elevator and Nozzle effect: With its highly advanced flight control software, the S/MTD coordinates the movement of the forward canards to give up-force, and the tailplanes and nozzles produce a down-force when maneuvering. This produces a pitching moment larger than that possible with the conventional elevator-only configuration. As a result, maneuverability is far improved.
But canards are contributors to an aircraft's total RCS and unlike weapons whose RCS contributions can be eliminated the canards' contributions are permanent. They have to be part of the original design conceptions and it will take very creative planforms to mask, not eliminate, their contributions.
only 3.5th 
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