Communications Requirements and Description

Communications Requirements and Functional Description

Subsystem Requirements

The Communication Subsystem (COMM) must:

Provide wireless transmission and reception of thermal and sun sensor data
Provide a means of activation of a payload
Be compatible with a common ground station
Fit within the constraints of the spacecraft structure
Interface with the Command and Data Handling subsystem
Run on +5V
Fit the budgetary constraints of the project

Functional Description

This system may divided into two distinct aspects: transmitting and receiving. The transmitter relays data collected onboard YODA to the ground station where the signal is processed and data translated into a form that may be interpreted by the user. The receiving side performs the complimentary process of gathering signals from the ground station and channeling these commands to the command center, the CPU.

The concept behind transmission is relatively simple. The CPU processes the signals from the sun and thermal sensors and using a 555 timer, represents these states as distinct frequencies. This signal is then passed to the COMM system. Here the data frequency is coupled with a carrier frequency (40 kHz) that is produced in a similar fashion using a 555 Timer. The frequency combined signal is then passed though a ULN2003 darlington with boosts the current and drives an IR LED which transmits the signal to a receiver on the ground station.

The primary components of the receiver are a 555 timer and a dual D flip flop. These are combined interpret a pulse signal sent from the ground station. The timer acts to strip the carrier frequency while the flip flop allows the ability to toggle between a high and a low signal which is carried back to the CPU. A series of logic gates are used to clean up the signal and prevent random toggling.

Links to Subsystem Documentation

YODA