Software Defined Radios For CubeSats.
My last blog talked about propulsion systems for CubeSats that used water as a propellant. These thrusters are a commercial product of a company called Tethers Unlimited. They have other products that are being marketed or being developed for space applications. One of these other products involves software defined radios for communication with and between satellites.
There are a number of bands in the electromagnetic spectrum that are assigned for use on satellites. These bands are regulated by the Federal Communications Commission or the Department of Defense for companies operating in the U.S. One of the problems for companies launching satellites is the time lag between applying for a frequency and receiving authorization. Traditionally, when a frequency is assigned, a crystal tuned to that specific frequency is installed in the radio receiver and transmitter. Sometimes the authorization comes so late that there are only days left until the satellite is scheduled to launch. This means that the satellite has to be taken apart and the crystal installed quickly.
Tethers Unlimited has developed a solution to this problem. Instead of a physical crystal that sets the frequency, their line of SWIFT radios use software to define the operating frequency. This means that the frequency can be set electronically prior to launch of a satellite without the need to disassemble the satellite. This results in savings in time and effort. The SWIFT radios are intended for use in CubeSats and other small satellites. They have AES-256 bit encryption built in.
The SWIFT radio series comes in several versions dedicated to different frequency bands. The family of SWIFT-SDRs includes:
SWIFT-UTX is used for UHF Satcom and Wideband TT& C frequencies. It is compatible with 10 watt UHF transmitter and a Dual-Channel UHF receiver.
SWIFT-SLX is used for S-band SGLS/USB/ISM transceivers. It is compatible with 10 watt UHF transmitter and a Dual-Channel S-band transceiver.
SWIFT-XTS is used for 300 Mbps X-Band Downlink + S-band SGLS/USB/ISM transceivers. It is compatible with 10 watt X-band transmitter and a Dual-Channel S-band transceiver. It is also compatible with an X-band receiver and a 10 watt X-band transmitter.
SWIFT-KTX is used for the K-band of frequencies. It is compatible with a 1 watt K-band transmitter and a K-band receiver.
All of the SWIFT software defined radios share a common software module referred to as SWIFT-LINK which "provides abstracted and frequency-agnostic multi-network, multi-channel, full-duplex communications support."
Tethers Unlimited also has systems that incorporate the software defined radios.
SWIFT-RelNav provides relative navigation, synchronization and inter-satellite communication for fleets of satellites without the need for an external reference signal.
SWIFT-AFSCN is a programmable SGLS/USB CubeSat radio that is used to communicate with AFSCN ground stations. It allows simultaneous reception on both the SGLS and USB bands and transmission on the S-band.
SWIFT-TacSatComm is a UHF CubeSat communication subsystem. It allows the satellites to communicate with military handheld radios.
SWIFT-WRX is currently under development. It is intended to permit CubeSats to receive a wide range of frequencies. The first model will handle frequencies from 50 MHz to 7 GHz. A future model will expand that to 50 MHz to 19 GHz.
While a few satellites might carry out their tasks without communications, for the vast majority of satellites, communications are critical to their purpose. Tethers Unlimited provides a wide ranges of software defined radios for use in space exploration and exploitation.
