A Unified Method for Solving the Frequency Plan of Space-Borne Software-Defined Radios

Software-defined radios (SDR) give space missions great flexibility by supporting diverse waveforms and mission scenarios. To configure and control this range of capability requires a model of the processing elements, both analog and digital. In this work we describe a unified method for solving and implementing the receiver and exciter frequency plans for a wide variety of hardware architectures. The flexibility of an SDRs frequency plan is enabled with programmable synthesizers and oscillators (e.g. DDS). Careful arrangement of these elements and band-selection filters is central to the hardware design. In the hardware design, up conversion and down conversion stages characterize the frequency plan for receive and transmit chains. Individual up conversion and down conversion stages can be segmented into a set of series or parallel blocks that completely represent the hardware design. Each stage can be fully characterized using a generalized converter block. We then formulate the frequency plan as a set of linear equations and solve the frequency plan with a single matrix operation. The converter stages also manage constraints on bandwidth and preferentially chose parameters to minimize spurious output. A block can also represent a reference oscillator or tunable DDS as part of a feedback control loop. The unified method can also accommodate a shared local oscillator between the receive and transmit paths. The end user can specify desired receive and transmit frequencies, and the method solves for all internal LO frequencies, or vice versa. The frequency plan solution is implemented in software and can be applied on any SDR platform. A notional configuration of the Frontier Radio for NASA's Europa mission is used as an example to demonstrate the methods.