A low-noise and scalable FPGA-based analog signal generator for quantum gas experiments

Achieving high fidelity for the measurement and control of quantum experiments imposes strict requirements on the precision and stability of surrounding electronics. Controlling electronics from a central device is more challenging when they are distributed in a laboratory and require analog signals where effects like ground loops and radiative cross-talk can limit their performance. Here, we present our design to address these challenges with a flexible and scalable analog signal generator. Our design is based on a field-programmable gate array (FPGA) development board, a custom PCB hosting a digital-to-analog converter (DAC) with 20 bit precision at 1 MSPS, and a custom breakout board. The FPGA development board accepts data from a master PC via TCP/IP where a user programs the waveform and sampling rate of each output channel and writes the data to on-board RAM. At runtime, the direct memory access (DMA) and Serial Peripheral Interface (SPI) modules inside the FPGA stream data to the custom DAC board via an Ethernet cable carrying the samples as differential signals along with the supply voltage. We designed the DAC board to be resistant to digital and analog noise by separating ground planes to prevent ground loops and by using high-precision and low-noise power supplies and voltage reference circuits. External trigger and clock inputs can be used to synchronize the DACs and multiple FPGAs. The time resolution and precision of our solution is optimized for experiments on quantum gases though it is flexible and can be adapted for many more applications.