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Tiny Tapeout Chip SDR Project: Combining an 8-bit ADC and an RF Mixer
0:00:01 Introduction: The video demonstrates a miniature software-defined radio (SDR) project using Tiny Tapeout 06 and 07 chips.
0:00:12 Project Overview: The project connects Coston Wolf's 8-bit ADC (Tiny Tapeout 06) with Collage's RF mixer (Tiny Tapeout 07) to create a functional SDR.
0:00:39 Signal Flow: An FM modulated signal from a signal generator is mixed down to a lower intermediate frequency (IF) using the RF mixer. The local oscillator (LO) for the mixer is generated by an RP2040.
0:00:58 Data Processing: The IF signal is then sampled by the ADC, the data is fed to a host PC running GNU Radio for demodulation.
0:01:08 Hardware Setup: A detailed explanation of the hardware setup, including the signal generator, a custom-designed board for signal conversion, the Tiny Tapeout boards, an oscilloscope, and a Glasgow Interface Explorer for data acquisition.
0:02:16 Bias: The bias is important to be set correctly as the differential air input of the mixer must be correctly biased.
0:05:16 Mixer Configuration: The presenter configures the Tiny Tapeout 07 board to use Collage's Gilbert cell mixer and sets the LO to 64 MHz (resulting in a 32 MHz LO at the mixer due to an internal divider).
0:06:25 Signal Generator Configuration: The signal generator is set to 32.5 MHz, creating a 500 kHz IF after mixing.
0:07:06 Bias Voltage: The bias voltage for the mixer's differential input is enabled.
0:07:25 RF Signal Verification: The RF signal from the generator is enabled, and a 500 kHz tone is observed on the oscilloscope, confirming the mixer's operation.
0:09:00 Bandwidth Limit: The oscilloscope's bandwidth limit is used to clean up the IF signal.
0:10:09 ADC Configuration: The Tiny Tapeout 06 board is configured to run the 8-bit ADC at 4 MHz.
0:11:03 ADC-Induced Spikes: Enabling the ADC introduces spikes in the spectrum at 4 MHz and its harmonics due to the capacitive nature of the ADC.
0:12:10 Data Acquisition: A Glasgow Interface Explorer is used to sample the ADC output and send the data to the host PC via USB.
0:12:56 GNU Radio Flowgraph: A GNU Radio flowgraph is used for FM demodulation. The flowgraph performs real-to-IQ conversion, spectral visualization, and FM demodulation.
0:13:37 SDR Introduction: For those that don't know, SDR stands for Software Defined Radio. It's not super important, but viewers are encouraged to learn more on their own.
0:15:20 Initial Demodulation: The flowgraph is started, and the received signal is displayed. Initial tuning demonstrates demodulation of a 400 Hz tone.
0:16:35 Demodulating Audio: Music from a phone is used as the modulation source, and successful FM demodulation is achieved.
0:17:53 Commercial FM Stations: The presence of commercial FM radio stations in the spectrum is noted, caused by the third harmonic of the LO (96 MHz) mixing with signals in the FM broadcast band.
0:18:55 Attempt to Demodulate Commercial FM: Attempts to demodulate the commercial FM stations are made but are not successful.
0:20:02 Antenna Limitations: The presenter notes limitations with the antenna and balun used, hindering the reception of the commercial FM signals.
0:20:49 Conclusion: The video demonstrates the successful creation of a basic SDR using Tiny Tapeout chips and highlights the potential for further development.