To optimize the performance of the dual-port antenna,we studied on the variations in lengths of the couplingpattern (LC) for CCSL and the gap in between couplinggap (CG). The parameters, LC and CG are illustratedin Fig. 2. Fig. 5 and 6 show the simulated S-parametersfor each signal port of dual-port antenna with respect tothe length of the signal port 2 pattern (LC) and the CG aspresented in Fig. 2. For the simulations, load impedance is setto 2.2 nH to congure the operating frequency to its lowestfrequency (e.g., 2.5 GHz). In Fig. 5 (b), LC is varied from 2 10 mm and CG isxed at 1.0 mm, which shifts the resonance frequency ofCCSL element from 2.65 to 2.4 GHz. In Fig. 6 (b), theresonance frequency of the CCSL element varies from 2.5 to2.15 GHz, as the CG is changed from 1.6 mm to 0.4 mm.This can be explained that the coupling pattern is a parasiticload capacitance seen by the CCSL radiator, and its value isproportional to LC but inversely proposal to CG. Therefore,the resonance frequency is detuned to the lower frequency asLC increases, and CG decreases. Note that changes of LC andCG do not impact on the S-parameters of the primary radiatoras shown in Fig. 5 (a) and 6 (a).Based on the simulation results, it is concluded that the LCshould be at least 6 mm and GC needs to be 0.71.5 mmto achieve good resonance characteristics. For the prototypedantenna, 1 mm is chosen for GC for the sake of simplicity andscalability of tooling the antennas in a lab environment anduse 6 mm of LC for resonance at 2.5 GHz. The same optimizationprocedure has been done for PIFA and its couplingpattern.Fig. 7 shows the simulated isolation properties betweentwo signal ports for several different LC-GC combinationswhich are chosen to keep the resonance frequency of theCCSL at 2.5 GHz. Note that the isolation near 2.5 GHzdecreases as the LC increases and this tells that LC shouldnot be too long. Recalling that the minimum LC is 6 mmto achieve a good resonance characteristic, 6mm of LC and1 mm of CG can be an optimal value for prototype antennarealization.