A Data Acquisition System for Kinetic-Inductance Detectors

Kinetic-inductance detectors (KIDs) combine high sensitivity with an intrinsic frequency-division readout capability. This kind of detector is ideal to build large arrays, which can be read out via frequency-division multiplexing. In order to precisely measure the detuning of the resonators, a highly specialized data acquisition system (DAQ) has to be used. We have developed a DAQ system, which is based on a XILINX Kintex 7 FPGA, with additional analog-to-digital/digital-to-analog converters. The analog signal chain is divided in a baseband with a bandwidth of 400 MHz and an RF band of 4-8.5 GHz, which can be adapted to different resonant frequencies of the detector array. To design a system with good linearity and noise performance, carefully selected analog components have to be used. To achieve a readout with video rate and high-frequency resolution, digital signal flow and signal processing are crucial. Therefore, clock synchronization is an important factor to achieve a dual-channel sampling rate of 1 GSPS. In order to obtain the upmost flexibility in signal processing, the digital signal processing is done completely in software on the PC. We will present the electrical characterization of the Kinetic-Inductance Readout Circuit (KIRC). Measurement results of a 20-pixel KID array will be shown and discussed in more detail.