Requirements:

While from a technical perspective the TI CC1120 appears to have the best performance and widest feature set, this chip appears to be out of stock until well into next year. The ADF7021 (as well as the ADF7021-V and ADF7021-N) meet requirements and have a decent number of chips currently in stock. Furthermore it is the chip used in this open source HAM project and is also used in AlbertaSat's open source design.

See sourcing sheet for detailed info on compared components.

Analog ADF series (i.e. ADF7021):

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Interfacing with this IC seems pretty straightforward. The chip has a 3 wire (+enable) serial interface used to configure settings such as modulation technique, output power, data rate, etc. Referring to the TR-7 firmware github repo the MCU uses GPIO pins and bit-bangs the appropriate commands to the chip.

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To actually transmit/receive data, the chip offers a couple different communication methods, however SPI mode appears to be the most versatile.

We can probably port over this arduino library for AX.25 for use with our MCU.

Further detail regarding supporting circuitry to be added soon (once I figure out how it works :P). Will be using the eval module, AlbertaSat's design and the TR-7 as a starting point. Once the RF section is designed, also plan to get Prof. R. Mansour to review.