Abstracts of presentations

• Synchronization for interferometry through White Rabbit (Paul Boven)

Radio interferometry is a technique where multiple receivers in different locations are coherently recording the same segment of the radio spectrum, in order to achieve a significantly improved angular resolution for the resulting image. Interferometer baselines in radio astronomy can cover a huge span of sizes, from meters to intercontinental distances, with the resulting resolution scaling with the observing wavelength and longest baseline length. Achieving sufficient phase coherence between all the receivers becomes more challenging as the distances and the observing frequency increase.

In this contribution I will discuss the requirements for coherence, and how these can be calculated from the performance of the reference clocks or clock distribution network, in terms of Allan deviation. This will then be illustrated by comparing this against the performance of the open hardware White Rabbit protocol, for existing and future radio astronomical interferometers. We have analyzed the performance of White Rabbit and improved its performance for long distance clock distribution. This has resulted in a successful demonstration of Very Long Baseline Interferometry (VLBI) observations using off-the-shelf software defined radio hardware and GNU Radio, synchronized through White Rabbit.

Slides of the presentation

• Multiheterodyne spectroscopy of Eu3+:Y2SiO5based on GNU Radio (X. Lin & al)
  

We report the use of GNU Radio to realize multiheterodyne spectroscopy of Eu3+:Y2SiO5crystal at cryogenic temperature. The flexible multiheterodyne scheme developed by GNU Radio also has the potential to be applied in other applications for precise physical state probing.

Proceeding of the presentation (PDF format)

Slides of the presentation

• Synchronization between a Vertical Incidence Pulsed Ionospheric Radar and an Ionospheric Echoes Receiver (Isaac Mario Tupac Davila)

In this presentation you will see how to synchronize a Vertical Incidence Pulsed Ionospheric Radar (VIPIR) and an Ionospheric Echoes Receiver (IER), made of an USRP N200, using GNU Radio Companion 3.8 and a generator pulse circuit, which will send one pulsed signal (trigger) in a specific time to beginning the transmission. It is used a GPSDO by the Ionospheric Echoes Receiver to set its time by NMEA's in the reception. Furthemore, you will see how the use of message passing and tags programmed in out of tree blocks affect the synchronization in the acquisition of ionospheric echoes.

Slides of the presentation

• Robust Reception for a Satellite-based Global Rescue System (Felix Artmann, Marcus Müller)

Saving lives is one of the most rewarding things you can do using SDR. In this presentation, we demonstrate a standards-compliant transceiver for the upcoming second generation of the COSPAS-SARSAT, and explain in depth how different approaches to frequency and phase synchronization can fundamentally improve receiver operational characteristics.

Slides of the presentation

• Hacking USRP gateware (Gwenhael Goavec-Merou)

Two Ettus Research USRP hardware platforms are investigated for adding custom functionalities to the FPGA gateware: the B210 on the one hand, and on the other hand the X310 through the RFNoC framework.

This presentation will demonstrate how to integrate a standalone, stream independant Verilog code either hand written or produced using Amaranth or LiteX, accessing Front Panel GPIOs for generating synchronization signals (1-PPS). A second demonstration will timestamp the datastream on an external synchronization signal.

SATRE is a proprietary modem commercialized by TimeTech and used for broadcasting pseudo-random sequences from ground to a geostationnary satellite for comparing clocks between time & frequency metrology laboratories. Similar to GPS, a digital communication code has been added on top of the CDMA code modulated as BPSK signals to transfer information including time and range from ground of each emitting station to the satellite. This signal is broadcast by European & American metrology institutes every even hours and decoding its content would open wide access to one-way time transfer, only requiring a television reception parabola and SDR receiver. Progress in decoding the code will be presented.

• An opensource framework for prototyping Two Way Satellite Time and Frequency Transfer using Software Defined Radio (Jean-Michel Friedt, Gwenhael Goavec-Merou & al.)
  

The current means of Two Way Satellite Time and Frequency Transfer relies on a closed, proprietary hardware developed in the 1980s and commercialized since by TimeTech GmbH with the SATRE modem. Beyond the little information available on the selected technology, few experiments have attempted to assess the limitation of current technological limitations, including coding length, coding scheme (BPSK) or pseudo-random sequence. We have developed an opensource portable framework for prototyping various means of selecting coding and modulation schemes aimed at assessing optimal conditions for sharing time and frequency in two-way communication, possibly adaptable to one-way communiction through the proposed open protocol. Preliminary results will be shared in addition to the technical details on signal acquisition and processing. 

Github: https://github.com/oscimp/amaranth_twstft

Slides of the presentation