Broadband HTS microstrip antennas for satellite communication

The major limitation of high-T/sub c/ superconducting (HTS) microstrip antennas is the narrow bandwidth due to the high Q and thin substrate. Defining bandwidth as the frequency range over which standing wave ratio (SWR) 2:1 or less, HTS antenna bandwidths are typically 0.85% to 1.1%. Thus considerable effort has been focused on developing antennas for broadband operation. In this work the HTS antenna, which consists of two triangle-radiation patches, was designed and fabricated using a YBa/sub 2/Cu/sub 3/O/sub 7-x/ (YBCO) superconducting thin film on MgO substrate for broadband operation. The input impedance and other characteristics for this antenna have been calculated using the moment method. Experimental results for our HTS antenna were reported in terms of radiation patterns, return losses, bandwidths and other various characteristics. The bandwidth obtained was a significant 6.7%.

l. Introduction

Superconducting thin films are increasingly applied for the manufacturing of diverse microwave device for the mobile and satellite communication [1]. The many and intensive researches on these microwave applications including filters, diplexers, delay lines and antennas have been reported until now [2] [3]. The use of superconducting transmission lines in the design of these microwave devices provides several benefits over their normal-metal counterpart. The advantage is a frequency independent penetration depth, which allows the implementation of compact designs with low dispersion. The lower surface resistance in HTS thin films compared to copper and gold, corresponds to high Q and improved performance such as lower insertion loss in passive microwave devices. Also the lower conductor losses in the HTS microstrip circuit give higher efficiency and superior performance of microwave passive devices.