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Blade Antenna-SDR System Prototype for the CANTAR Global 21-cm Experiment: Simulations, Measurements, and In-Situ Results

F. P. Mosquera, J. Rodriguez-Ferreira, E. Acevedo, O. Restrepo, D. Gonzalez, G. Chaparro

TL;DR

This work designs, simulates, and tests a low-frequency blade-dipole radiometer with an SDR backend for global 21-cm cosmology in the 100–200 MHz band. By combining an EDGES-inspired blade antenna, a dual-stage LNA front end, and configurable SDRs (LimeNet Mini, E310, USRP), the authors quantify impedance, beam chromaticity, and spectro-temporal stability through HFSS simulations and on-site measurements. The Ettus E310 offers the best balance of sensitivity and linearity among SDRs tested, achieving system temperatures near $T_ ext{sys} \approx 443$–$453\ \mathrm{K}$ with filtered amplification; radiometric estimates indicate potential sub-$\mathrm{mK}$ sensitivity with 1000 h integration under ideal calibration. The results establish a viable path for site-testing and foreground characterization in Colombia and Antarctica, informing further calibration, filtering, and long-term deployments toward calibrated global 21-cm measurements.

Abstract

We present the design and initial testing of a low-frequency radio telescope prototype developed for the CANTAR (Colombian Antarctic Telescope for 21-cm Absorption during Reionization) experiment. Operating from 100 to 200 MHz, the system integrates a blade dipole antenna inspired by the EDGES high-band design with a software-defined radio (SDR) receiver. We report simulations of antenna impedance and beam chromaticity, along with SDR performance tests (Limenet Mini, Ettus E310, USRP2920). A dual-stage low-noise amplifier reduces system temperature, enabling foreground-sensitive observations. Radiometric estimates suggest sub-mK sensitivity is achievable with 1000 h of integration. This prototype forms part of Colombia's emerging infrastructure for 21-cm cosmology, with deployments planned in low-RFI sites in the Colombian Andes and Antarctica.

Blade Antenna-SDR System Prototype for the CANTAR Global 21-cm Experiment: Simulations, Measurements, and In-Situ Results

TL;DR

This work designs, simulates, and tests a low-frequency blade-dipole radiometer with an SDR backend for global 21-cm cosmology in the 100–200 MHz band. By combining an EDGES-inspired blade antenna, a dual-stage LNA front end, and configurable SDRs (LimeNet Mini, E310, USRP), the authors quantify impedance, beam chromaticity, and spectro-temporal stability through HFSS simulations and on-site measurements. The Ettus E310 offers the best balance of sensitivity and linearity among SDRs tested, achieving system temperatures near – with filtered amplification; radiometric estimates indicate potential sub- sensitivity with 1000 h integration under ideal calibration. The results establish a viable path for site-testing and foreground characterization in Colombia and Antarctica, informing further calibration, filtering, and long-term deployments toward calibrated global 21-cm measurements.

Abstract

We present the design and initial testing of a low-frequency radio telescope prototype developed for the CANTAR (Colombian Antarctic Telescope for 21-cm Absorption during Reionization) experiment. Operating from 100 to 200 MHz, the system integrates a blade dipole antenna inspired by the EDGES high-band design with a software-defined radio (SDR) receiver. We report simulations of antenna impedance and beam chromaticity, along with SDR performance tests (Limenet Mini, Ettus E310, USRP2920). A dual-stage low-noise amplifier reduces system temperature, enabling foreground-sensitive observations. Radiometric estimates suggest sub-mK sensitivity is achievable with 1000 h of integration. This prototype forms part of Colombia's emerging infrastructure for 21-cm cosmology, with deployments planned in low-RFI sites in the Colombian Andes and Antarctica.

Paper Structure

This paper contains 31 sections, 7 equations, 17 figures, 11 tables.

Table of Contents

  1. Introduction
  2. Methods
  3. System Requirements
  4. Role of SDR Technology
  5. Radiotelescope System Description
  6. Antenna and Ground Plane
  7. Receiver Architecture and SDR Integration
  8. Signal Processing and Software Architecture
  9. Antenna simulations
  10. Results
  11. $S_{11}$ Response
  12. Beam Chromaticity
  13. System Characterization Measurements
  14. Antenna Reflection Measurements
  15. SDR Linearity and Sensitivity
  16. ...and 16 more sections

Figures (17)

  • Figure 1: Subsystems of the radiotelescope to be validated.
  • Figure 2: 100-200 MHz blade antenna. Schematic of the antenna (left), blade antenna in-situ at Páramo de Berlín (right).
  • Figure 3: Software architecture using GNU Radio.
  • Figure 4: $S_{11}$ simulations for the blade antenna considering 5 balun heights.
  • Figure 5: Blade antenna chromaticity simulation for a balun height @ 22.5 cm. Gain change for the $\phi = 0^\circ$ (left) and $\phi = 90^\circ$ (right) planes.
  • ...and 12 more figures