Essay Example on How to design an efficient C band transponder to be used in Femto satellite








PROPOSED WORK WITH METHODOLOGY The C band covers the frequency range between 4 to 8 GHz The transponders operating at this frequency range are called C band transponders The basic transponder locks onto a constant carrier uplink tone and generates a constant carrier downlink tone which is phase coherent with the uplink aluminum shells present in the transponder maintains rigidity of the structure and provides electromagnetic shielding The power supply unit we use in this proposed transponder is a transformer coupled DC DC converter and it supplies regulated voltages to the transponder and its subsystems The down converter is used to supply the frequency conversion and the gain required for the functioning of the transponder In this there are two local oscillators that are made to get locked to a predetermined reference given by the coherent detector Variable gain amplifiers present in the down converter are also a subsystem of the automatic gain control AGC function The coherent detector reference generator consists of a final frequency translation stage It converts to a baseband signal which are meant to control the frequency control loop and the automatic gain control loop AGC The control voltage of the frequency control loop is used to tune a low noise voltage controlled crystal oscillator to keep track on the uplink carrier This reference is used to develop a down converter local oscillator signals and the coherent downlink carrier Like this uplink and downlink phases are kept in matching lockstep The functionality of this includes carrier detect circuitry and special switched bandwidth loop filters The transmitter has a local oscillator locked to the precision reference signal and a RF power amplifier

The control unit is a microcontroller programming all the phase locked loops and sets the default transponder state as power up It also performs basic control and telemetry interfacing with the spacecraft control systems A simple RS 232 serial link CENTRE FOR TECHNOLOGY DEVELOPMENT AND TRANSFER Student Innovative Project 2017 18 Proposal Report SIP ID 1617S4063 Page 1 of 7 is provided for ground testing SPECIFICATIONS Uplink frequency of the proposed transponder 7 15 7 19GHz Downlink frequency of the proposed transponder 8 4 8 45GHz Tx Rx ratio of the proposed transponder 880 749 Tx RF power of the proposed transponder 3W Acquisition power level of the proposed transponder 134dBm Tracking power level of the proposed transponder 134dBm 140dBm Typical IF bandwidth of the proposed transponder 3 5kHz Power supply of the proposed transponder 26 32v Noise figure of the proposed transponder 3dB IMPLEMENTATION The subsystems of the transponder are as follows 1 Power supply unit 2 Down converter 3 Coherent detector reference generator 4 Transmitter 5 Control unit Parameters like antenna gain transmitter power receiver sensitivity provide a reliable path to meet our objectives CENTRE FOR TECHNOLOGY DEVELOPMENT AND TRANSFER

Student Innovative Project 2017 18 Proposal Report SIP ID 1617S4063 Page 1 of 7 Antenna positioning and tracking equipments are adjustable to compensate for positional variation in the satellite Physical structure are designed to withstand the harsh climates The radome or de icing equipment makes sure that the transponder functions properly during snow or icing conditions Outdoor Equipment An antenna for has a low noise amplifier for reception and a down converter for converting microwave to intermediate frequencies For transmission additional equipment is required an upconverter for converting frequencies from intermediate to microwave frequencies and a solid state power amplifier for boosting signals for transmission Antenna Configuration Low Noise Blockconverter Since the transmitted signal travels a vry long distance it is very weak at the time of reception it is amplified to a range that can be used for communication A low noise amplifier achieves this without burying the transmitted signal with internal amplifier noise Most ground stations today utilize solid state low noise amplifiers comprising field effect transistors FETs made of from gallium arsenide GaAs a semiconductor material 

This device is less noisy extremely rugged and relia WORK PLAN To design the mixer amplifier filters present in the downconverter and the coherent detector reference generator transmitter section of the transponder EXPECTED OUTCOME RESULTS The femto satellite with proposed transponder is expected to function as a better communication satellite with efficient size and cost APPLICATIONS C band transponders are widely used for the telemetry telecommand control of satellite This requires full protection from all other external interferences such as risk of losing control C band is used to enhance the air traffic control systems in areas where land coverage is unreliable The CENTRE FOR TECHNOLOGY DEVELOPMENT AND TRANSFER Student Innovative Project 2017 18 Proposal Report SIP ID 1617S4063 Page 1 of 7 interconnection between the remote VHF towers and the air traffic control centre is given by C band FSS systems C band can supply the required reliability for safety services It is not preferred to be replaced using other bands it withstands all climatic conditions imposed on it It provides Sufficiently high reliability in tropical and high rain regions CONCLUSION Thus with all these above furnished details and the gained knowledge we will be able to design an efficient C band transponder to be used in Femto satellite FINANCIAL

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