Modular Design of RF Front End for a Nanosatellite Communication Subsystem Tile Using Low-Cost Commercial Components

Abstract

In recent years, the development market for low-cost nanosatellites has grown considerably. It has been made possible due to the availability of low-cost launch vectors and the use of “commercial off-the-shelf components” (COTS). The satellite design standardization has also helped a great deal to encourage subsystem reuse over a number of space missions. This has created numerous opportunities for small companies and universities to develop their own nanosatellite or satellite subsystems. Most COTS components are usually not space qualified. In order to make them work and withstand the harsh space environment, they need extra effort in circuit redesign and implementation. Also, by adopting the modularity concept and the design reuse method, the overall testing and nonrecurring development cost can be significantly reduced. This can also help minimize the subsystem testing times. The RF front-end design presented in this paper is also considered one of the better and feasible choices based on the above approach. It consists of an S-band transceiver that is fully implemented using COTS components. In the transmit chain, it is comprised of the transmitting CC2510 RF matching network and a power amplifier (PA) with an RF output power of up to 33\u2009dBm which connects to an antenna using two RF switches. The receive chain starts from the antenna that is connected through two RF switches to the low-noise amplifier (LNA) that further connects to the receiving CC2510 via the RF matching network. The receiver sensitivity is -100\u2009dBm. This is a half-duplex system using the same antenna for transmitting and receiving. The receiver and transmitter chains are isolated together using two RF switches which together provide an isolation of up to 90\u2009dB at 2.4\u2009GHz. The concept behind using two RF switches is to provide better isolation from the transmit chain to the LNA. The matching network of CC2510 has been designed in a symmetric fashion to avoid any delays. All the RF COTS used have been selected according to link budget requirements. The LNA, PA, and RF switches were tested individually for compliance. The passive components used in the overall design of the matching network are chosen on the basis of minimum dimension, least parasitic behaviour, and guaranteed optimum RF matching. Also, the RF COTS used are non-CMOS which makes them more robust against space radiations associated with the LEO environment and enables them to provide a radio communication data rate of up to 500\u2009kbps in both uplink and downlink. The vacant spaces on the implemented PCB are shielded with a partial ground plane to avoid RF interference.