APPROX FL220 DSNDING; THE RPTR IN A B737 ENCOUNTERED B747 WAKE TURB.

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DSNDING ON ARR TO ZZZ TO CROSS INTXN AT 250 KTS AT 11000 FT. AIRSPD 280 KTS AT APPROX 2000 FPM DSCNT. NO TA'S FROM CENTER. ACFT ENTERED A SLIGHT BURBLE THEN SUDDENLY ROLLED L ABOUT 10 DEGS; MORE BURBLE; THEN ACFT ROLLED FURTHER L 20-25 DEGS. DISCONNECTED AUTOPLT IMMEDIATELY COUNTERED ROLL AND AT SAME TIME PULLED UP; STOPPED ROLL AT 30 DEGS WITH AGGRESSIVE CTL INPUT WITH BOTH AILERON AND RUDDER. FO AND I SUSPECTED WAKE TURB BUT CTR HAD GIVEN NO ADVISORIES. ONLY AFTER HDOF TO APCH DID WE HEAR THE OTHER ACFT AND WERE TOLD TFC TO FOLLOW WAS ACR XXX HVY; 15 MI IN FRONT. ACR XXX WAS A B747 CARGO. SEEMS WE WERE ON SEPARATE CTR FREQS UNTIL APCH. WE HAD HEARD CTR TALKING TO ACR BUT ONLY CTR PORTION OF CONVERSATION. WE WERE UNAWARE THAT WE WERE IN-TRAIL AND I SUPPOSE CTR HAS NO OBLIGATION TO ADVISE BEYOND NORMAL SEPARATION. I'D BE HAPPY TO DISCUSS THIS FURTHER. IT IS STILL VERY VIVID IN MY MIND TO SAY THE LEAST! FLT ATTENDANTS CAME FORWARD TO INQUIRE AND LATER SOME OF THE PAX MENTIONED THE INCIDENT UPON DEPLANING. APPARENTLY CONDITIONS WERE STABLE ENOUGH TO ALLOW THE VORTICES TO REMAIN INTACT UNTIL WE HIT THE R WING TURB. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED HE HAD THE SEAT BELT SIGN ON BECAUSE HE ALWAYS TURNS THE SEAT BELT SIGN ON AT TOP OF DSCNT. THE AUTOPLT WAS ON AND HIS FEET WERE FLAT ON THE FLOOR AND NOT ON THE RUDDER PEDALS. AT FIRST HE CAUGHT A LIGHT BURBLE WHICH HE NOW RECOGNIZES AS THE SIGNATURE OF AN IMPENDING WAKE ENCOUNTER. HE THEN ENCOUNTERED AN UNCOMMANDED 10 DEG BANK FOLLOWED BY ANOTHER BURBLE AND AN ADDITIONAL 20-25 DEG BANK WHICH PUT HIM IN ABOUT A 35 DEG BANK. DURING THIS BANK HE DISCONNECTED THE AUTOPLT; SHALLOWED THE DSCNT; AND EXITED THE WAKE USING AGGRESSIVE AILERON AND ELEVATOR. THE FACT THE WAKE TURB WAS AN INDUSTRY ISSUE PROMPTED THE RPTR TO SUBMIT HIS RPT. HENCE; THE 5 MONTH DELAY IN SUBMITTING THE RPT.