arXiv subjects

Roger John Hoyland

Publications and source records attributed to Roger John Hoyland.

3 recordsLinked to original sources

arXiv2026

Calibration electronics for the 30 and 40 GHz instrument (TFGI) of the QUIJOTE experiment

The 30 and 40 GHz instruments of the QUIJOTE radio astronomy experiment use very sensitive receivers which need to be characterized both to ensure their proper functioning and for their calibration. Given the age of the PXI-1031DC device used up until now for this purpose, the design of a new device, the Calibrator TFGI QUIJOTE, has been proposed. This new device has been designed with the idea of being simple and modular, easy to use and upgrade. It is built on a Raspberry Pi 5 system, using an MCC 118 as analog reading module. This system, widely known among both makers and professionals, not only meets the requirements of modularity and ease of use, but also ensures that the device is much more economically competitive than the PXI. A first version of the device has been built and tested, obtaining good results in accuracy and ease of use.

astro-ph.IM↗

arXiv2026

A high-isolation wideband channelizer for MKID readouts: a custom HLS implementation on RFSoC

We present a high-performance channelizer for Microwave Kinetic Inductance Detectors (MKIDs), designed to mitigate spectral leakage and scalloping loss through a 50% overlapping polyphase filter bank (PFB). The design is implemented on a Xilinx Zynq UltraScale+ RFSoC ZCU111 using a custom design - primarily in Vitis High-Level Synthesis (HLS), with the time-critical output serializer and glue logic in VHDL - that processes a 4.096 GSPS input stream with a per-branch super-sample rate (SSR) of 16. Rather than relying on aggressive 512 MHz clocking and vendor IP cores, our split-path architecture computes the delayed and non-delayed polyphase branches concurrently, so that the bulk of the channelizer operates at a robust 256 MHz while a single 512 MHz subdomain is confined to the BRAM-to-FFT section. This architectural parallelism enables a deep 16-tap prototype filter that doubles the filter depth of comparable high-speed systems and substantially improves channel isolation. We report the complete internal architecture of the reordering engine that implements the overlap, including two implementation hazards not documented in prior art: a pipeline-stage skew affecting state toggles in HLS, and the state-preservation requirements of a restartable design. The 2/1 overlapped channel response is validated in simulation - recovering the ~3.9 dB scalloping loss of a critically sampled channelizer to below 0.1 dB across the full 2 MHz channel - and characterized systematically with a 100-tone batch frequency sweep, while the parent readout system has been operated cryogenically with an MKID array in an adiabatic demagnetization refrigerator (ADR), identifying individual resonators in total darkness. The result is a resource-efficient, high-isolation benchmark for wideband frequency-division-multiplexed readouts.

astro-ph.IM↗

arXiv2026

QUIJOTE-TFGI polarization calibration -- Ground characterization and on-sky validation with Tau A and the Moon

Our objective is to characterize the QUIJOTE Thirty and Forty GHz instrument (TFGI), calibrate it with a reference calibration signal on the ground, compare our results with on-sky calibration based on bright sources, and study the stability of the calibration parameters over time. First, from the ground, we fit the data using a reference calibration signal (a diode) introduced to resolve degeneracies among the various instrument angles. Finally, we utilize on-sky observations of Tau A and the Moon to validate the results. By creating calibration datasets obtained with the reference diode, we evaluate the data quality and quantify phase switch errors to account for the fine polarization response. We also utilize Tau A and Moon observations to calibrate the system's response and stability over time. In addition, we calculate the refraction index of the Moon to be $n_{Moon}$ = 1.209 $\pm$ 0.007 (stat) $\pm$ 0.005 (sys) at 31 GHz under smooth-surface assumption. The results from fitting the instrument phase-switch error angle align with 0 deg at 2$σ$ precision, indicating that no further correction is required within a few percent precision. The calibrations with astrophysical sources (Tau A and the Moon) yield consistent results that constrain the polarization angle and responsivity. The polarization efficiency aligns well with ground measurements and the Tau A characterization, whereas the Moon-based calibration is more affected by systematics. We find hints of responsivity variations over time, although the relative responsivity between channels is found to remain stable. In the future, we conclude that installing a live calibrator will enhance performance by continuously monitoring responsivity and, in turn, improving the mitigation of systematic effects.

astro-ph.IM↗