Hawaii Center for Advanced Communications

Fig. 1b shows a practical and commercial utilization of this technology. For the proposed work, the standard low loss material between the parallel plates will be replaced by a multi-layer dielectric that includes Ferroelectric materials sandwiched between two low loss dielectric layers as shown in Fig. 1c. DC biasing of the Ferroelectric materials change the dielectric constant, the effective electrical distance between the array elements (stubs), and hence the beam steering capability. Fig. 1c shows the proposed multi-layer dielectric placement in the feed structure of a three elements array. It should also be noted that the Ferroelectric material layer will be removed from under the aperture feed of the radiating stubs and preliminary simulation results show that this will decrease the sensitivity of the array performance to tolerances in the fabrication process, and hence contribute to the low cost feature of this technology. Fig. 1d shows the simulated resulting radiation pattern at 2 GHz for two cases of the Ferroelectric materials tunability values of 10 and 20 %. Unlike the work our group reported in an earlier publication [1], it is expected that the inclusion of the multilayer structure will result in a significant reduction in losses, increase of the input impedance to values of practical interest, and acceptable level of reduction in the effective tunability and the ability to steer the beam. Initial simulation results are given in Table II. As it may be seen this was actually the case as the insertion losses may be reduced by a factor of 100, while maintaining about 85 percent of the original tunability. These results are truly significant but certainly need experimental verification.

TASKS & DELIVERABLES

• We are actively engaged with the modeling and simulation of the phased array antenna system which includes the multilayer dielectric approach integrated with Barium Strontium Titanate (BSTO) BaxSr1-xTiO3 (BSTO) Ferroelectric materials. The multilayer dielectric approach will be examined for reduction in conductor losses while maintaining antenna tunability and impedance.

• • Prototypes of the antenna array to verify the modeled results. These designs will be fed by H-plane sectoral horn and will involve dc bias stubs for biasing the Ferroelectric material and changing the dielectric constant. Designs will be performed at X-band for the easy availability of the test and measurement equipment.

• Individual prototypes will be constructed to test, characterize, and optimize the biasing of the Ferroelectric material in a single and multilayer environment.

REFERENCES

1 M. F. Iskander, Z. Yun, Z. Zhang, R. Jensen, and S. Reed, “Design of a low-cost 2-D beem-steering antenna using Ferroelectric material and the CTS technology,” IEEE Transactions on Microwave Theory and Techniques, vol. 49, no. 5, pp. 1000-1003, May 2001.

2 M. F. Iskander, Z. Zhang., Z. Yun, R. S. Isom, M. G. Hawkins, R. Emrick, B. Bosco, J. Synowczynski, and B. Gersten, “New Phase Shifters and Phased Antenna Array Designs Based on Ferroelectric Materials and CTS Technologies,” IEEE Trans. Microwave Theory and Techniques, Vol. 49, No. 12, pp. 2547-2553, Dec. 2001.