A new binary version of Particle Swarm Optimization called Boolean PSO (BPSO) is applied in order to design current dividers that distribute the current to three output ports and resonate simultaneously at three frequencies. The BPSO is based on the negative selection, which is one of the basic processes in an Artificial Immune System (AIS). The optimizer must satisfy specific requirements at all resonant frequencies, concerning the impedance-matching bandwidth and the distribution of the complex current on unmatched real or complex terminal loads. The dividers are considered to feed mobile communications antenna arrays and are optimized for GSM/DCS/UMTS operation. The optimization is performed by applying both the BPSO and a conventional PSO. The comparison shows that the BPSO is more efficient because it has the ability to produce structures with better frequency response.