In the comparison in Table III, the antenna proposed in this study uses
three switches to achieve 23 states, which is the
maximum number of reconfigurable states. Compared with previous FRAs,
this antenna has a smaller size and achieves more states using fewer
switches.
In far-field situation, the proposed antenna aims to maintain
bidirectional radiation characteristics in the E-plane (yz-plane) and
nearly omnidirectional pattern in the H-plane (xz-plane) for all the
eight states, which is in accordance with the far-field patterns of
typical printed MMA. This work is tested in an anechoic chamber. Fig. 6
shows the simulated and measured far-field results at state 111, where
radiation patterns are most possibly changed because of the dc supplies
for the three switches. The simulated far-field results still agree well
with the measured output. The simulated gain for all states varies from
1.11 dBi to 1.59 dBi, where the peak gain is obtained at state 000
because all switches are turned off, and the radiation efficiency is
larger than 84%. However, the measured peak gain is 0.5 dBi because the
p-i-n diodes and many lumped elements introduce some losses.
Conclusion: A 3-bit frequency reconfigurable meander-line MMA is
proposed. The antenna has 23 = 8 independent narrow
band states. The number of states is optimally large in terms of the
number of switches used because of the antenna’s binary
reconfigurability. The measured results agree well with the simulated
ones, and good impedance matching characteristics and acceptable
bandwidth are achieved on each state, covering a considerable frequency
range from 1.01 GHz to 1.54 GHz. This antenna has similar far-field
radiation characteristics as the traditional MMA and features in
immensely miniaturized size.