Its simple; phased array antennas such as use on the spy-1 S-band radar system are easily jamable when confronted with a two point jamming signal that is out of phase and widely spaced. It usually uses two jamming antennas spaced about 35 feet apart mounted on the wing tips of the jet. See the attached Chinese paper on cross eye jamming and how it works.
The Iranians use this on there F-5 jets by mounting jamming pods on the wing tips where the missiles usually go. This is a known problem with any phased array radar antenna system. Such as now being used on the f-22 and the f-35 and the B-2. The same trick is used to jam conical scan radar systems too.
The Achilles heal of the AEGIS cruisers is the fact that it has no good old fashion ppi scan radar antenna to fall back on. Only the X-band Phalanx system can be used as a back up. They will have to retrofit all of the AEGIS cruisers with an auxiliary mast mounted radar antenna with mechanical ppi scan to fix the problem.
This is why the Russians know that stealth is a waste of time. Cross eye jamming is cheaper and it works better. Also the Patriot missile system is in danger to this type of jamming. So the NATO ballistic missile defense system has just been defeated by the Russians.