This paper presents the design of an upconverter system based on Commercial Off-The-Shelf (COTS) components for the 17.3-21.2 GHz space-to-Earth Fixed Satellite Services (FSS) frequency band, with a variable Intermediate Frequency (IF) up to 4 GHz. The proposed system combines Upper SideBand (USB) and Lower Side-Band (LSB) frequency conversion modes and Local Oscillator (LO) leakage nulling techniques to enhance Spurious-Free Dynamic Range (SFDR). LO leakage nulling was used to show that it is possible to improve a minimum 31 dBc SFDR in the FSS bandwidth to 48 dBc. The upconverter was connected to a 10 W power amplifier, limited in the 17.3-20.2 GHz band, and its performance was compared with the International Telecommunication Union (ITU) recommendation on spurious emissions. The system is compliant for all the RF bandwidth within IF band 2.5-3.5 GHz and in the RF sub-band 17.8-20.2 GHz for IF band 3.5-4.0 GHz. The proposed system was then evaluated at sample RF and IF frequencies in terms of Error Vector Magnitude (EVM).

This paper proposes a Ka-band receiver front-end for future CubeSats Low-Earth Orbit (LEO) to Geostationary (GEO) inter-satellite links. The receiver is able to support very high data rates (up to 100 Mbit/s) in Quadrature Phase-Shift Keying (QPSK) when in the line of sight of a GEO satellite that is equipped with a steerable 70-cm antenna and transmitting a 25-W signal. The originality of the proposed approach is twofold. First we will demonstrate the receiver feasibility based on a class of miniaturized and low-cost microwave integrated circuits, currently available on the market. In particular, our receiver is based on a novel combination of integrated Low-Noise Amplifiers (LNA) with an image rejection filter, the latter exploiting the Substrate Integrated Waveguide (SIW) technology. An optimization of the via placement proved to be able to reduce the need for shielding apparatuses, thus simplifying the mechanics and reducing mass, volume and hardware costs. Secondly, we will propose a noise injection circuit capable of measuring and calibrating the receiver gain, also during in-orbit operation. Self testing capabilities are particularly relevant for CubeSats because the usage of commercial components poses serious reliability issues.