Communications Subsystem - Big Pico
|For the communications subsystem, we decided
to continue using the transmitter and power amplifier circuitry used on
the small pico. Since the big picos would take the scientific data, we
needed a modem to modulate the data and a receiver to pick ground commands
telling the satellites to collect lightning data. The modem chip is the
Texas Instrument TCM3105 and was discontinued
a couple of years ago. You might ask, then how did they get the TCM3105?
Well, you still might find them in a Packet Radio Kit made by Ramsey Electronics
(model number P-IBM), which are found at your local electronic surplus
store. We used the chips and the crystals, that came with the kit, and
modified the modem circuitry for our comm subsystem.
Here is one of the test comm boards for our big picosatellite.
|We needed a receiver that was easy to implement
with little time. Initially, we looked at Motorola
and RF Micro Devices for receivers but
realized we did have the experience nor the knowledge to test and debug
the circuitry. Then we looked at RF Monolithics
single-chip receiver. These receivers are low power, running off 3.0 volts
and 1 mA. The RX1000 uses OOK (on-off keying) or ASK (amplitude shift keying)
|Please see the comm schematics and trade-off sheet.|
Please view the information on the comm system of Small Pico.
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