Design

The CAPE1 communications subsystem consisted of a TNC (Terminal Node Controller), Transceiver, RF Amplifier and Antennas. A Microchip PIC18LF452 microcontroller acts as the TNC, which will create and decode the AX.25 protocol which contains the team’s data. The transceiver being used is the Chipcon CC1020, which was chosen because of its extremely small size, low power, and low cost. The CC1020 gives the CAPE team the ability to communicate with the satellite.

For CAPE2, the communication team will develop a forward error correction (FEC) encoder onboard the TNC to enhance telemetry with coding gain. Due to the difficulties with the CC1020, a new radio will probably be researched.

TNC

A TNC takes the data to be transmitted and encodes the data based on the AX.25 protocol. See Paccomm devices. The CAPE1 TNC employed the Microchip PIC18LF452 microcontroller.

Firmware

Firmware documentation for the flight version of the communications system firmware resides at http://svn.jonathanwagner.net/cape/CAPE1/Communications/Software/Documentation/trunk/latex/refman.pdf (right-click and save as).

The code is available for anonymous subversion checkout at http://svn.jonathanwagner.net/cape/CAPE1/Communications/Code/ and can be browsed by clicking the link in your browser.

Radio

Here are some ideas for CAPE 2 radio:

Transmitter/Receiver ICs

Single Chip Transcievers

Chipcon CC1000 is the radio first tested by CalPoly.

Chipcon CC1020. This is the radio employed on CAPE 1.

Analog Devices AD8346. QAM quadrature modulator. Could prove useful for other ISM bands.

Si4210 Aero II (datasheet). Although probably not applicable for cubesat, it is a device for GPRS solution on board a small sat. Still pretty neat.

RF Amplifier

The RF amplifier used on board was RF Micro Devices RF2117 (obsolete). The following RF amp design was used on CAPE1. What is most obvious is the large amount of filtering designed around the device.