Realization of a microstrip-aperture-coupled-passive-liquid patch antenna

Abstract

A novel concept of using electrically conducting liquids/fluids (including biological fluids such as Plant Sap [Bionics]) and the technique of utilizing the property of thermal expansion, for the design and development of Passive RF/Microwave circuits and functions have been studied and reported [6,7]. Various passive microwave functions such as electromagnetic radiators (Microstrip Antennas), passive components (Interdigital Filters) and transmission lines (Coaxial and Microstrip) have been realized and successfully demonstrated along with working prototypes [1-5] earlier. In this paper we communicate and report the successful development of a rectangular liquid patch microstrip antenna using liquid: mercury as the radiating element in the X-Band. Mercury being the radiator of electromagnetic signals, in our case. We also called it as ldquothe Liquid Patchrdquo. The making, that includes: the construction and fabrication of this antenna with ldquomercuryrdquo as ldquothe liquid patchrdquo is somewhat similar to the conventional Physician's temperature-measuring instrument: Mercury Thermometer. The distinguishing features of this liquid patch antenna system is that, its characteristics may be switched, varied and controlled by exercising suitable control over external temperature/s. The technology, mechanisms and techniques involved in the development of the liquid patch antenna has been discussed and also highlighted in this paper. Utilization of the above techniques and principles have shown that its possible to affect changes in realtime on critical antenna parameters, such as: resonant frequency, VSWR, Bandwidth, Radiation Pattern and Polarization. The same has been demonstrated and confirmed here practically. This novel technique, to change the characteristics of such antenna systems may perhaps be explored and utilized to our advantage, under certain existing environment and strategic situations/conditions. This liquid (mercury) antenna was fabricated and tested at the Antenna Fabrication and Test Facility. Space Applications Centre - Indian Space Research Organization, Government of India, Ahmedabad.