Fig. 5. Photograph of the proposed 3-bit FRA.
Results and discussion:The measured results of the reflection coefficient and the photograph of the antenna prototype are given in Fig. 4 and Fig. 5. The S11 results are measured with an Agilent N5230A vector network analyzer. Eight independent states are observed with the operating frequency switched from 1.04 GHz to 1.51 GHz. Good impedance matching and low return loss are obtained for each state, and the simulated and measured working frequency and bandwidth at each state are compared in Table II. Except for a small frequency shift of approximately 74 MHz on average for each state, agreement between the simulation and the measurement results is good. The measured bandwidths are larger than the simulated ones, and this is possibly caused by the resistive loading of the biasing components and switches in practical designs. Furthermore, Fig. 4(a) shows a few unexpected perturbations on the S11 curves caused by the parasitic effect of biasing lumped elements. Fig. 5 gives a photograph of the fabricated prototype antenna.