Delfi-n3Xt Communication Subsystem
The Primary Transceiver (PTRX) and ISIS Transceiver (ITRX) are a redundant set of radios for continuous operations designed and provided by ISIS BV. The ITRX is slightly different from the PTRX with improved power efficiency and an interface to a linear transponder module for radio amateur communication. This module is a cooperative development between the TU Delft, University of Twente and ISIS BV and transponds all signals from a 40 Khz bandwidth received on the UHF to the VHF dowlink. It will be activated once the major experiments have been performed.
The antenna system for the primary transceivers contains a set of four antennae in a turnstile configuration. This configuration ensures a near-omnidirectional pattern such that the primary radio communications is independent of the performance of the attitude control subsystem. An advanced phasing circuit is designed which also isolates the transmitter from the receiver effectively and connects to both PTRX and ITRX. The VHF/UHF antennae are custom designed in Modular Antenna Boxes (MABs) which are similar to Delfi-C3. All this is integrated on a board which also hold the deployment circuitry for the MABs and the solar panels. The electrical design is a cooperation between TU Delft and T-minus Engineering BV.
The experimental S-band transmitter will be used to demonstrate relatively high data rates for CubeSats. All data sent by the PTRX or ITRX is sent out by the STX as well in a continous beacon mode. All data is also stored in local flash memory. The STX can be requested to resent the packets of a specific time window to obtain missing packets from times in which there was no ground station able to receive the telemetry from the primary transceivers. A patch antenna is integrated on the same PCB of a small form factor of about 4 cm x 4 cm: the whole radio is located in the side margins of the structure of the satellite. The directional antenna should be pointed toward the ground station for an optimal data link.