This paper presents a feasibility study for a very high data rate receiver operating in the K/Ka-band suitable to future Moon exploration missions. The receiver specifications are outlined starting from the mission scenario and from a careful system analysis. The designed architecture uses a low noise front-end to down-convert the incoming K/Ka-band signal into a 3.7 GHz intermediate frequency (IF). For maximum flexibility, a software defined radio (SDR) is adopted for the I/Q demodulation and for the analog to digital conversion (ADC). The decoding operations and the data interface are carried out by a processor based on field programmable gate array (FPGA) circuits. To experimentally verify the above concepts, a preliminary front-end breadboard is implemented, operating between 27.5 and 30 GHz. The breadboard, which uses components off the shelf (COTS) and evaluation boards (EVBs), is characterized by a 46 dB gain, a 3.4 dB noise figure and a − 37 dBm input-referred 1 dB compression point. Finally, a 40 Msym / s quadrature phase shift keying (QPSK) signal is demodulated by means of a commercially available SDR, demonstrating the above concept. The importance of these results is that they have been obtained exploiting a class of miniaturized and low cost microwave integrated circuits currently available on the market, opening the way to a dense communication infrastructure on cislunar space.

Advanced applications of the finite element method use hybrid meshes of differently shaped elements that need transition cells between quadrilateral and triangular faced elements. The greatest ease of construction is obtained when, in addition to triangular prisms, one uses also pyramids with a quadrilateral base, as these are the transition elements with the fewest possible faces and edges. A distinctive geometric feature of the pyramid is that its vertex is the point in common with four of its faces, while the other canonical elements have vertices in common with three edges and three faces, and that is why pyramids' vector bases have hitherto been obtained with complex procedures. Here we present a much simpler and more straightforward procedure by shifting to a new paradigm that requires mapping the pyramidal cell into a cube and then directly enforcing the conformity of the vector bases with those used on adjacent differently shaped cells (tetrahedra, hexahedra and triangular prisms). The hierarchical curl-conforming vector bases derived here have simple and easy to implement mathematical expressions, including those of their curls. Bases completeness is demonstrated for the first time, and results confirming avoidance of spurious modes and faster convergence are also reported.

Singular divergence-conforming bases have been proposed for the solution of integral equations although they have seen only occasional use in practical applications. The existing singular bases are not hierarchical, which prevents their use in adaptive p-refinement applications. In this paper, a new family of singular hierarchical basis functions is proposed for quadrilateral cells. These functions model the singularities associated with current and charge density at edges and are more convenient for modeling such singularities than triangular bases of the same kind. The basis functions are of the additive kind and combine a hierarchical polynomial representation on quadrilaterals with linearly independent singular terms that incorporate general exponents that may be adjusted for the specific wedge angle of interest. Moreover, the added singular basis functions are computed on the fly. On the basis of various reported numerical results, this paper also illustrates the difficulties, the advantages, the accuracy, and the cost of using such bases in the method of moment solutions of integral equations.Index Terms-Basis functions, hierarchical basis functions, method of moments (MoM), singular basis functions, wedges.

The use of singular basis functions enhances the convergence of method-of-moments (MoM) solutions for structures containing edges. While standard algorithms for computing the MoM matrix entries treat Green's function singularities, these are not well-suited for integrating the singular basis functions: conventional quadrature routines exhibit slow convergence and may produce inaccurate results. In this paper, new algorithms are proposed for handling the combination of edge singularities and Green's function singularities on quadrilateral cells.

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