Long wave antenna design for CALLISTO System

Abstract

Life on the surface of the earth is highly affected by solar activities. The real time observations of these solar activities are highly important to minimize the effect on the earth system. Solar radio observations are relevant to the study of such phenomena. The Compound Astronomical Low-frequency Low-cost Instrument for Spectroscopy and Transportable Observatory (CALLISTO) system is one method to study the solar radio bursts. This paper highlights a new study leading to the development of a long wave antenna (LWA) design, which is proposed for a new CALLISTO station. Generally, the solar radio bursts are circularly polarized and more often observed in low regions of the high frequency (HF) and very high frequency (VHF) bands. Therefore, the antenna is designed for the frequency range of 20 MHz to 100 MHz. The designing of the antenna was done using 4nec2 software, a Numerical Electromagnetics Code (NEC) based antenna modeller and an optimizer. The main structure of the design contains two identical antennas in both north-south and east-west directions. The performance of the design was tested by changing the dimensions and simulating the model to optimize the parameters. Considerable performance increases could be observed by applying the ground plane to the antenna model. The resulting performance by simulation shows average gain test (AGT) values of 1.923 at 15 MHz, 2.001 at 30 MHz, 2.021 at 50 MHz, 2.056 at 70 MHz and 2.096 at 100 MHz. The 1.90 - 2.10 AGT range ensures the model is perfect with the input parameters for the physical production. The maximum gain was obtained as 9.12 dB at 50 MHz and in the frequency range considered, this design could maintain a gain higher than 7 dB. The other important performance factors, voltage standing wave ratio (VSWR), structure loss, efficiency, left-hand circular polarization (LHCP) and right-hand circular polarization (RHCP) gain, etc. are also observed. From the simulations, it was observed that LHCP gain is always dominating total gain.