HALF E SHAPED 3×3 ANTENNA ARRAY FOR SATELLITE COMMUNICATION IN X BAND

Abstract

To understand about our universe scientists have been putting a lot of efforts by doing space exploration. People are keen to know more and more about the evolution in this field. They feel excited by not only knowing about the technologies used in current exploration but also they want to know what’s coming next. They want to know every technology that is needed for space exploration missions. The data about mars reaches earth by using high gain antenna which has ultrahigh frequency band. It is attached to a spacecraft send on mars. The frequency used by this antenna is X band frequency. This full system is mainly used directly from the earth by up linking the commands and downlinking the small telemetry data on earth. The currently used high gain antenna gives gain of about 25 dB in X band. Due to long distance communication a lot of losses occur in the form of large space loss of direct to earth link and low radiated power that is effective to transmit data to earth. Now for future missions a high performance communication system is needed that are direct to earth linked. But this up gradation requires large antenna system and large power amplifier. Making an antenna which gives good power handling property and higher gain and that to in X band will give higher data rates and greater flexibility. According to the antennas used during mars exploration the high gain antenna used for enhanced direct to earth (DTE) communication a lot of requirement are understood for future exploration. To improve the expedition these improvement are necessary as it will enhance the potential of high gain antennas (HGA) currently being used. Requirements are as follows:  Right hand circularly polarized output (RCP);  Tramsition gain of above 30 dBic at a frequency of 8.6 GHz.;  The operational frequency band should be of 70MHz of bandwidth which would be centered at 8.6 GHz frequency;  Volume of antenna should be less than 38*38*5 centimeter cube. The main reason behind making this antenna was the size of antenna as heavy and large antennas make it difficult in stowage during launch, cruise, entry, descent and landing. For interoperability of antenna with deep space network earth station circular polarization was

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chosen. Polarization alignment and atmospheric effects like Faraday rotation are also reduced with circular polarization. The complete structure consists of small patches subarray which will be fed with a waveguide divider. This enables high power handling from the transmitter. The requirements of circular polarization, fabrication friendly for X band frequencies and dual band will be fulfilled with this circular polarized subarray. The antenna formed has 9 different patches. Each patch is provided with a separate feed. That is total 9 coaxial feeds are applied with each feed equal to 1W. This structure gives high gain and also works in two different bands s band and x band. It can be converted as per the use. It has low return losses. Substrate used is roger and it makes it light weight. The complete structure is smaller than current used antennas used in mars navigation. It can further be turned into single feed by applying a waveguide power divider which provides power to each patch. This will further reduce the power consumptions. Half E shape of patch gives high gain with required bandwidth. A sorting bar enables the mode to radiate in x direction instead of z direction. After analysis in HFSS of all three antennas we came to conclusion that in single patch half E antenna the resonant frequency is 9.2 GHz. Frequency band is from 8.97GHz to 9.34 GHz. The return loss of this antenna is -19.21dB; efficiency of this antenna is 96%; gain received is 7.9 dB and VSWR is 1.2 dB.

For 2×2array half E shaped patch antenna has resonant frequency 8.6 GHz; Frequency band is from 8.38GHz to 8.87 GHz; the return loss of this antenna is -25.6; efficiency is 98%; gain is 11.1 dB; VSWR is 1.1.

For 3×3 array half E shaped patch antenna resonant frequency is 8.6; Frequency band is from 8.7GHz to 9.7 GHz; return loss of this antenna is -20.37 dB; antenna efficiency is 96%; gain of antenna is 31.7 dB and VSWR is 1.4dB.