B737-800
Air Traffic Control Fully Certified
Other / Unknown; Situational Awareness
ATC Issue All Types; Deviation / Discrepancy - Procedural Published Material / Policy
General None Reported / Taken
ATC Equipment / Nav Facility / Buildings
B737-800 was vectored to an ILS Runway 16L approach and cleared for such. B737-900 was vectored in behind B737-800 with the intent to conduct a dual dependent ILS approach to Runway 16R. I had established vertical separation while vectoring the B737-900 onto the final approach course. We were using 'FUSED' RADAR display which has an undesirable characteristic of 'target hopping'; an erratic flight path. I misjudged the distance and turned the aircraft in too close to successfully complete the approach. I broke him off to the southwest when I determined it would not work out. Separation was lost during the escape maneuver. FUSION RADAR sometimes causes a track to display as much as 1/2 mile from actual position. I have seen 'jumps' into adjacent finals followed by accurate depiction of aircraft position. I misjudged rate of turn and wind effects in this situation. [I need to] be more conservative in vectoring aircraft into position for dual-dependent ILS approaches; particularly during wind conditions such as were present.
S46 Controller expressed concern regarding the operational characteristic of 'FUSED' RADAR; noting the targets 'jump' making it difficult to insure proper instructions are issued.