# Wideband Versatile Receiver for CubeSat Microwave Front-Ends
## 1 Introduction  
Since the first CubeSat launch in 2003, approximately 2.000 CubeSats have been sent into outer space [1, 2]. The exponential growth of the number of CubeSats can be attributed to the great interest of both space agencies and private companies. Above all, the research activities of academic teams are fueled by the cost-effectiveness of CubeSats compared to bulkier satellites [3]. Moreover, the availability of commercial off-the-shelf (COTS) components, easily accessible with a limited budget, fueled the research activities in the space sector. CubeSats are compact and lightweight nanosatellites characterized by sizes complying with the standard dimensions of 10 cm \(\times\) 10 cm \(\times\) 10 cm for a single unit. The Cube represents a standard unit (U-), which must weigh less than 1.33 Kg. A maximum number of 24 units can be assembled to obtain complex structures with advanced performance [4]. The requirement of complying with standard dimensions must not be intended as a limitation. Indeed, the designer can take the opportunity to send a CubeSat into outer space by joining existing launch opportunities, where a dedicated section is available to carry nanosatellites of standard dimensions. This aspect contributes to keeping down the launch costs. In a satellite communication system, one of the most critical stages is represented by the receiver. This is a consequence of the changing landscape of applications and technologies based on satellites developed in recent years [5]. Nowadays, a whole set of applications are based on concepts such as the Internet of Things (IoT), machine-to-machine (M2M) communications and smart-everything services, e.g., the possibility to provide connectioncapabilities in remote locations. As an example, by equipping a CubeSat constellation with IoT communication systems, it would be possible to establish a connection with IoT ground-segment sensors placed in remote locations, otherwise inaccessible from ground communication systems. Developing such a service requires more bandwidth to be available for the user [6; 7; 8]. In this scenario, designing wide bandwidth receivers represents a critical hardware requirement for satellite-based approaches. In the scientific literature, many research activities focused on a manifold set of topics concerning CubeSat receivers can be found [9; 10; 11; 12; 13; 14; 15; 16; 17; 18; 19; 20; 21; 22; 23; 24; 25; 26]. The most relevant related contributions are reported and briefly described in Section 2. It is worth noting that these works show only operating bandwidths narrower than the 2-18 GHz bandwidth of this contribution. This allows the authors to highlight the main technological limitations of the current receivers, represented by the difficulties in obtaining wide working bandwidths by maintaining low spurious levels without significantly increasing the cost of the system. To fill this gap, in this contribution, a microwave down-converter is proposed as a multi-purpose CubeSat receiving stage. The performance of the circuit was first simulated within the Cadence AWR Microwave Office design environment software in order to accurately select the required components and tune the final system behavior. The complete receiving chain has been designed with the aim of creating a compact system easily integrable into nanosatellite front-ends. Particular attention has been paid to keeping down the costs by using COTS components. The proposed topology uses a dual-conversion architecture exploiting two local oscillators (LOs) stages to provide a severe reduction of both the number and level of spurious in the operating band. Indeed, the first up-conversion stage allows us to filter the signal at a higher frequency, whereby the filtering task can be accomplished more effectively, i.e., with a better spurious rejection [27]. Finally, the signal was down-converted to the baseband in order to be processed more comfortably.