# Characterization of a COTS-Based RF Receiver for Cubesat Applications +
## 2 The Method Extension  
The RF receiver was designed to operate with a 2025-2110 MHz input frequency range to be compliant with the European Cooperation for Space Standardization. A design flow, typically adopted in the aerospace context, was followed. Starting from the mission analysis, a minimum set of system requirements was defined, which constituted the starting point of the design, especially in the choice of the most suitable architecture. The superheterodyne architecture was adopted for the receiver design. The architecture foresaw a single conversion stage to minimize the number of the components. The RF incoming signal was downconverted to the Intermediate Frequency (IF) by a COTS RF mixer, amplified, filtered, and finally output through a coaxial connector. With respect to the traditional architecture, some improvements were implemented to meet the noise figure and input dynamic range requirements. The noise performance has been improved by cascading two low-noise and high-gain COTS amplifiers before the preselector filter, which allowed a drastic decrease in the total noise figure. Likewise, two cascaded adjusted gain control COTS amplifiers were placed at the end of the receiver chain, which allowed to obtain a gain variation dynamic of 52 dB that, besides fulfilling the input dynamic range requirement (-115--70 dBm), also added 7 dB of margin. In conference paper [17], we focused on the modelling aspects of the system. The receiver model was made considering not only the nominal functional performance but also the performance in the worst-case. We pointed out that the \"worst case\" is not easily identifiable; therefore, it was implicitly assumed in the system requirements. For example, if the noise figure must be smaller than 3 dB by requirement, such requirements must be valid even in the presence of radiation and thermal changes. Another assumption was that the RF parameters drift from the nominal value because of frequencies, operating temperature, and total ionizing dose. The amount and the signs of such drift were not known a priori, because of the lack of reliability data. Since the final target of the receiver is to amplify the incoming signal to a fixed output power of 0 dBm \(\pm\) 1 dB (by requirement) and since the RF parameters suffer a drift, as previously assumed, we implemented a worst-case analysis based on the Monte Carlo analysis that allowed to estimate the total net gain and noise figure of the whole receiver, starting from the variation of the RF parameters of each individual component. Such an estimation was performed assuming a safety margin that considered both lack of reliability information and the lack of the specific tests on the evaluation boards, i.e., using only the data reported in the datasheets, even if they were less accurate. The safety margin was set at 10%, resulting from a reasonable hypothesis on the components' behavior when studying their technology. The system simulations showed that all requirements were satisfied. The most relevant result was in the output power level, which was equal to 0 dBm even in the presence of net gain variations that exceed the minimum required input dynamic range (45 dB). In other words, the Monte Carlo analysis has shown that the 7 dB of margin obtained by the AGC system can compensate any drift in the output signal power level. The assumption that RF parameters only suffer a drift may be too conservative. Especially concerning radiation, we cannot exclude a priori the possibility that the ionizing radiation could cause permanent damage to the components. Therefore, the components' behavior can be definitively predicted only by performing a component level radiation test. Such a target has been reached and presented in this manuscript. The adopted method is based on the experimental tests designed to be performed even in the final phases of the project.