This is the Google/EFabless/Skywater Caravel submission of the Amateur Radio Satellite Transceiver.

These blocks serve as the first pieces in a larger design of an open source amateur radio satellite transceiver - this is the first tapeout submission.

The design sources of the continued project can be found here: amsat_txrx_ic.

VCO Layout

A S-Band phase locked loop employing a differential ring oscillator VCO with quadrature outputs. CML (Current Mode Logic) and flip-flop based pre-scaler dividers are used with a fractional-N divider which uses a 3rd order MASH structure with dithering. Finally a PFD (Phase Frequency Detector) is combined with a charge pump with off chip filtering to complete the loop.

A cell based buffer is used to drive the external 100 ohm differential output.

Bandgap Layout

A bandgap reference with separate PTAT and CTAT currents. Provides less than +/-0.2% variation from -40 to 125 degrees celcius (tt simulation). 6 bits of trimming on both PTAT and CTAT allows less than 1% accuracy over process variations.

To install the environment used for development of this repository, follow these instructions.

1. Install the tools:

git clone https://github.com/yrrapt/sky130_setup.git
cd sky130_setup
./install_pdk.sh
./install_tools.sh

2. View schematics:

cd amsat_txrx_ic-caravel/xschem
xschem

3. View layout:

cd amsat_txrx_ic-caravel/gds
klayout caravel.gds

4. Run DRC:

cd amsat_txrx_ic-caravel/utils
./run_drc amsat_txrx_ic-caravel

5. Run LVS:

cd amsat_txrx_ic-caravel/utils
./run_drc amsat_txrx_ic-caravel