Many of the Current Spacecraft Missions Are Designed for a Specific Task Requiring Specialized

Many of the current spacecraft missions are designed for a specific task requiring specialized hardware that is unique to that specific craft. In order to minimize costs, designs must be versatile enough that they can be reused for different applications yet specific enough that mission goals can be accomplished. In communications traditional RF hardware is very much customized to the frequency, output power and mode of communication used. These customizations result in a new communications system developed for each band and mode. To create a universal radio it would have to support a wide range of frequencies and modes with little to no additional hardware. Recent advances in digital signal processing and digital to analog conversion are making it possible to design such a radio where all of the signal generation is produced and/or decoded in a DSP or FPGA by software. The goal of this project is to create a radio that can be incorporated in multiple satellites that have different communication specifications as well as have the ability to change their communication methods after deployment by a software upgrade.

To achieve a universal space grade reconfigurable radio it must satisfy a wide variety of specifications commonly used in space applications. Frequencies used in space range from just above DC to 10 GHz or more. A successful radio will have to encompass a majority of that range with adequate radiated power for each band. The radio will also have to communicate in many different modes such as PSK, FSK, ASK, OFDM, CDMA, FM, AM, GFSK, QPSK, GMSK and a host of others. Another requirement is that it is able to be upgraded via software when new modes are standardized and used. To facilitate the ability to switch modes and frequencies a high speed high transistor count FPGA will be used to digitally create and receive signals. This FPGA will be broken into sub-blocks that each contains a different modulation or demodulation method. These blocks can then be linked to any output or input frequency or to each other to create a variety of options. While at first there seems to be little need for blocks to be connected in series, say for example an AFSK signal that can be created by using FSK into FM. The FPGA would then be connected to both an analog to digital converter (ADC) and a digital to analog converter (DAC). The ADC allows for signals to be fed into the FPGA while the DAC allows for transmitting signals. Using current DAC and ADC technology with at least 12 bit resolution frequencies up to approximately 30 MHz can be directly transmitted and received. For frequencies higher than 30 MHz the signal must be mixed down to a lower frequency. For each band a separate intermediate frequency (IF) section and filtering section needs to be made with the ability to be switched in and out of the circuit at will for both transmit and receive. A variety of antenna systems could then be switched into the system. The radio will also have the ability to act as a cross band repeater and even as a converter switching one type of signal on a certain frequency to a different mode on another frequency. This feature would allow dissimilar systems to be linked without new hardware being purchased for either user. With the possibility of putting blocks on the FPGA in series it would be simple to integrate encryption methods into a block allowing signals to be encrypted outside of a CPU an thus saving processing power.