Integrated direct RF sampling front-end for VHF avionics systems

For a market sector where size, weight, power and cost (SWaP-C) optimization is crucial, specifically with the proliferation of unmanned aerial systems, this paper proposes the minimization of SWaP-C requirements through a Direct RF Sampling (DRFS) approach. This work focuses on the integration of avionics systems operating at the VHF band, i.e. VOR, ILS (LOC and GS) and aeronautical communications (voice, ACARS, VDL, etc.). The scope of this work is to present a feasibility study of the proposed integrated avionics. Several factors must be taken into account: First, the selection of a best sampling frequency is a key point in the design of the system. Two approaches to sampling frequency selection are considered: 1) static, whose aim is to digitize and lock the frequency bands fully; and 2) dynamic, where only the occupied channels are sampled without aliasing. The second important factor to be considered in addition to sampling frequency refers to the maximum dynamic range of the system. The dynamic range of the Analog to Digital Converter (ADC) has to be large enough to receive without distortion the most and the least powerful signals at the antenna. Finally, this work studies the digital down-converter (DDC) architecture to be hardware implemented in a Field Programmable Gate Array (FPGA), and quantitatively analyzes the resources required for its implementation.