NIKEL: Electronics and data acquisition for kilopixels kinetic inductance camera

Abstract

A prototype of digital frequency multiplexing electronics allowing the real time monitoring of microwave kinetic inductance detector (MKIDs) arrays for mm-wave astronomy has been developed. Thanks to the frequency multiplexing, it can monitor simultaneously 400 pixels over a 500 MHz bandwidth and requires only two coaxial cables for instrumenting such a large array. The chosen solution and the performances achieved are presented in this paper.the analog bandwidth and the number of detectors (resonators) managed by the electronics must be maximized. At this respect, we present here a building block for the NIKA camera [1,2] that is able to monitor simultaneously 400 pixels over a 500 MHz bandwidth. Instrumentation methodologyThe instrumentation setup used for NIKA and its associated electronics is extensively described in [9]. In summary, the excitation frequency comb is generated at baseband in the electronics using coordinate rotation digital computer (CORDIC), up-converted with an IQ mixer to the 1 to 10 GHz frequency and injected in the resonator line. The returning and thus modified frequency comb is down-converted and analyzed by channelized Digital Down Converters (DDC) to determine each tone amplitude and phase. Aside from good signal to noise ratio (SNR) on the whole chain, the first limitation on the number of MKIDs managed by this solution is given by the digital to analog converter (DAC) and the analog to digital converter (ADC) bandwidths. The second constraint comes from the computing power limitation. For a FPGA (Field Programmable Gate Array), the computational power is determined by the available amount user logic and multiplier block times their maximum running frequency. Indeed, thanks to the inherently achievable parallelization in FPGAs, this figure is much larger compared to DSPs that have only a few Multiplier Accumulators.Starting from the previous version, which was able to manage a line of 128 tones over a bandwidth of 125 MHz, three solutions are possible to increase the multiplexing factor per line. The first solution would be to juxtapose several of the previous electronic boards, each one managing its share of bandwidth, see figure 1.Unfortunately, the analog filters required to separate each share of bandwidth before downconverting have such a stringent separation requirement to avoid crosstalk due to image frequencies that they cannot be constructed.The second option is to use faster ADCs an DACs combined to a larger computing power (FPGA) in order to directly cover a larger bandwidth. Following this path, two concurrent approaches still remain. The first "obvious" solution is to directly generate the frequency comb at twice the desired bandwidth and to perform channelized DDC with the ADC signal. Unfortunately, due to the frequency limitation of state of the art FPGAs this can only be achieved by performing massive design pipelining on both sides, excitation and analysis, and therefore makes it extremely complicated.The third option, which we have chosen, is to use modern DACs feat...

Performance and calibration of the NIKA camera at the IRAM 30 m telescope

“…Such standing waves were also responsible of the larger dips that are observed before adding the bondings, and they disappear afterwards. Bourrion et al (2012b), are capable of generating up to 400 tones each over a 500 MHz bandwidth. This is achieved by using six separate FPGAs: five of them generate 80 tones each over a 100 MHz band, using five associated DACs.…”

“…These detectors are designed to be read out with frequency-division multiplexing with a large multiplex factor from a few hundred to several thousand per readout chain Bourrion et al (2012a); Swenson et al (2010) and are relatively simple to fabricate (see for example Day et al 2003;Doyle et al 2007). This technological solution has been selected for the NIKA project (Monfardini et al 2010(Monfardini et al , 2011 consisting of a dual-band millimeter camera for observations at the 30 m Institut de RadioAstronomie Millimétrique (IRAM) telescope (Pico Veleta, Spain).…”

Bi-layer kinetic inductance detectors for space observations between 80–120 GHz

“…We used a vector network analyser (VNA) to measure the LEKID responsivity and the NIKEL electronics (described in Bourrion et al 2012) to measure the spectral response and characterise the noise. The NIKEL electronics has been successfully used during several NIKA observing campaigns (Catalano et al 2014;Adam et al 2014).…”

Non-parametric deprojection of NIKA SZ observations: Pressure distribution in thePlanck-discovered cluster PSZ1 G045.85+57.71

“…Of particular importance is the clarification of the physical origin of this normalization and scatter in the scaling relations, rendering the use of galaxy clusters for cosmological application more robust. The New IRAM KIDs Array (NIKA; Monfardini et al 2011;Bourrion et al 2012;Calvo et al 2013) was a dualband continuum camera operated at the Institut de Radio Astronomie Millimetrique (IRAM) 30 m telescope between 2010 and 2015. It was one of the very few tSZ instruments with sub-arcminute resolution.…”