(a) (b) (c) (d)
Fig. 2. Surface current distributions for state 001 (a),
state 100 (b), state 101 (c), and state 111 (d).
Antenna Configuration and Miniaturization Design:
Fig. 1 shows a miniaturized binary frequency-reconfigurable meander-line
antenna. The main transmission line of the antenna is folded three times
at different locations. Three meanders have uniform width.
As shown in Fig. 1, three PIN diode switches are introduced at the
meander of the main transmission line, and short narrow strips extended
from the meanders are used to place PIN diodes. By switching on the PIN
diode switch, the relevant parts of the bending structure with different
lengths are bypassed from the antenna structure. The current flows
directly from the PIN switch without passing through the bypassed
transmission line section, resulting in a shorter actual path length of
the current. Consequently, the operating frequency of the antenna
increases. On the contrary, the corresponding parts are connected to the
antenna structure by turning off the switch. For example, when the PIN
diode D1 is turned on, the BP1 section is bypassed, and
the current passes directly through the switch D1without going through BP1. As a result, the actual path length of the
current is shortened, and the frequency of the antenna is
correspondingly increased. Different settings of the on/off status of
D1, D2, and D3 result in changes in the effective length of the antenna,
which can achieve 23 different operating frequencies
and realize frequency reconfigurability.
As
for the biasing circuit, C1, C2,
C3, C4, and C5 achieve
DC-blocking, dividing the antenna into multiple transmission line
segments with different DC voltages. In1 and
In2, as RC chokes, are connected to ground via holes and
achieve DC grounding as one end of the PIN diodes D1,
D2, and D3. The three control voltages,
V1, V2, and V3 are
respectively connected to the other end of D1,
D2, and D3 via inductors
In3, In4, and In5.