ACR CAPT REPORTS PHANTOM TCAS ALERT AND RA WHILE CLIMBING OUT. ATC REPORTS NO TRAFFIC IN THE VICINITY. CIRCUIT BREAKER RESET ELIMINATES PROBLEM.

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THE FO WAS FLYING. SHORTLY AFTER BEING HANDED OFF TO DEP CTL WE WERE CLRED TO FL200. THROUGH APPROX 5000 FT WE WERE IMC. SHORTLY THEREAFTER WE RECEIVED A YELLOW TCAS ALERT. THE SCREEN INDICATED A TARGET AT OUR ALT AND JUST OFF OUR L SIDE (LESS THAN A HALF MI). I HAD THE FO TURN R 30 DEGS. WE THEN RECEIVED A RED TCAS ALERT. SAME TARGET. I ASKED DEP CTL IF HE HAD ANY KNOWN TFC IN OUR AIRSPACE. AT THE SAME TIME WE RECEIVED A DSCNT COMMAND FROM THE TCAS. THE FO STOPPED THE CLB. DEP CTL SAID THAT THERE WAS NO TFC IN OUR AREA. ALL THAT WAS NEARBY WAS A TARGET AT OUR 11:30 O'CLOCK POS AND 10 MI CONVERGING. DEP ASKED OUR HDG. I RESPONDED WE WERE HDG 230 DEGS. DEP TOLD US TO TURN L TO A HDG OF 180 DEGS FOR THE TFC. AS WE WERE MAKING THE TURN; I HAD THE FO PULL AND RESET THE TCAS CIRCUIT BREAKER. DOING THIS CANCELED THE TCAS ALERTS. I PERFORMED A SELF TEST WHICH WAS NORMAL. WE CONTINUED THE TRIP WITHOUT FURTHER INCIDENT. WE COULD THINK OF NO VALID REASON FOR THE ALERTS. UPON RETURNING I CHKED WITH MAINT TO SEE IF THEY HAD ANY SUGGESTIONS FOR THE ALERTS. THE AVIONICS TECH SAID THAT HE HAD ONLY HEARD OF IT HAPPENING ONCE BEFORE. IT WAS SHORTLY AFTER THE CREW ENTERED IMC JUST AS WE HAD. BUT HE DID NOT HAVE ANY EXPLANATION; BUT HE WOULD DO SOME RESEARCH AND GET BACK TO ME.