The design and characterization of gap-coupled high-T/sub c/ superconducting microstrip patch antennas

Thin-film high-temperature superconductors (HTS) have found use in many different applications since their discovery in 1986. Their popularity is due in great put to the advances in deposition technology, which has provided high-quality films on a variety of substrates. For the most part, the primary advantage of using superconducting materials in antenna systems is the reduction of the loss associated with transmission line matching circuits, filters, and feed networks particularly at microwave and millimeter-wave frequencies where ohmic losses begin to significantly affect the system´s performance. For large antenna arrays with long, elaborate corporate feed networks, the use of HTS transmission lines can substantially increase the gain of the antenna arrays. The efficiency of the individual microstrip patch antennas is limited by the power dissipated by ohmic losses in the patch element and ground plane, the dielectric loss in the supporting substrate, and the undesirable excitation of surface-wave radiation. Because the surface-wave excitation increases with increasing substrate thickness and permittivity, the substrate upon which the microstrip antenna is patterned is typically electrically thin (less than 0.01/spl lambda//sub 0/). Unfortunately, there is a substantial decrease in the radiation efficiency on thin substrates, which is due to the conductor and dielectric loss. These losses can be significantly reduced by constructing the antenna from thin films of HTS materials on low-loss substrates. We summarize our efforts in investigating the properties of superconducting microstrip patch antennas.