Simulated and Measured Results

The simulation is performed using Ansoft HFSS while the measurement is taken by an Agilent E8362B performance network analyzer. The patterns of the proposed antenna are measured in a 7.0 x 3.6 x 3.0 m3 anechoic chamber with the NSI far-filed measurement software. The proposed antenna is fabricated on a FR4 substrate with a dielectric constant of 4.4 and thickness of 0.8mm. The loss tangent of substrate is 0.02. The optimized parameters

Appendix B. Frequency Reconfigurable Slot Antenna Using PIN Diodes

are as follows: W1=13.75, W2=W3=3.95, W4=4.75, W5=9.7, W6=1.4, S=1, L1=37, L2=1, unit mm. The overall dimension of the proposed design is 26.4 x 40 mm2. In the following design Infineon BAR64-02V PIN diodes are used, with a forward resistance of 2.1ohm, a reverse parallel resistance of 3000 ohm, a diode capacitance of 0.17pF, and a lead inductance of 0.6nH. The value of Cp1 and Cp2 are 2.2pF while the Lbias is 100nH.

Fig. B-2. Return loss of proposed antenna. (a) LR mode. (b) RR mode.

Fig. B-2 exhibits the simulated and measured return loss at the RR mode and the LR mode. As shown in the figures, the agreement between the simulation and measurement is

Appendix B. Frequency Reconfigurable Slot Antenna Using PIN Diodes

interference from the dc bias lines and connecting cable, as well as from the diodes model used in the simulation. The proposed antenna can operate at different frequencies by controlling the positions of the diodes.

(a)

( )b

Fig. B-3. Simulated current distribution. (a) LR mode. (b) RR mode.

2.0 2.5 3.0 3.5

-35 -30 -25 -20 -15 -10 -5 0

ReturnLoss(dB)

Frequency (GHz)

Sim. LR mode Sim. RR mode Mea. LR mode Mea. RR mode

Fig. B-4. Return loss of proposed antenna at W¹=W⁴=13.75mm

Appendix B. Frequency Reconfigurable Slot Antenna Using PIN Diodes

The simulated current distribution at RR mode and LR mode are shown in Fig. B-3. It is obvious that they both closed follow a quarter sinusoidal pattern with the maximum current concentrated in the forward state diode and the minimum current in the open-end slot. It should be mentioned that the two modes share very similar properties and the antenna structure can be applied in other operating frequencies.

According our design concept, the proposed antenna is not only treated as the frequency reconfigurable antenna, but also is treated as the pattern reconfigurable antenna when both length of slots at right side and left side are equal. The Fig. B-4 shows the measured and simulated return loss of proposed antenna when left side structure is as same as right side structure of the antenna. In this case, at RR mode and LR mode, the operating frequencies are both 2.45 GHz. and the wave radiates to opposite directions.

Fig. B-5 exhibits the simulated and measured radiation patterns of the RR mode and the LR mode in xy-,and yz-plane. The measured patterns agree with the simulation results. The measured gain in the yz-plane at RR mode (2.45 GHz) and the LR mode (2.9 GHz) is -0.6 dBi and 0.093 dBi, respectively. The measured gains are slight lower than the simulated ones, mainly resulting from the PIN diodes and DC bias network. the cross-polarization levels are generally much lower than the co-polarization ones. The proposed antenna also show good front-to-back ratio at yz- and xy-plane.

B.4 Conclusion

A frequency-reconfigurable slot antenna has been proposed in Appendix B. By carefully controlling these diodes, the antenna behaves conventional λ¸/4 slot antenna. According to the length form the open-end slot line to the microstrip line and the position of the forward state diode, the proposed antenna can operate at assigned frequencies with opposite radiated

Appendix B. Frequency Reconfigurable Slot Antenna Using PIN Diodes

ones. The maximum radiated gain is around 0.93 dBi for 2.45GHz and 0.95 dBi for 2.9 GHz.

The proposed antenna may apply in various forms of the wireless communication.

Appendix B. Frequency Reconfigurable Slot Antenna Using PIN Diodes

Fig. B-5. Simulated and measured radiation patterns. (a) xy-plane. (b) xz-plane. (c) yz-plane.

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