MAPPERR Multi-frequency Radar
Guidelines for building MAPPERR: a towable, coherent, ground-based, ice-penetrating radar
At its core MAPPERR, the Multi-frequency Active-Passive Exploration Radar-Radiometer, is a software-defined radio (SDR)-based ice-peentrating radar that runs Open Radar Code Architecture (ORCA). Operable as a snowmachine-towed radar, MAPPERR is one of the few coherent ground-based ice-penetrating radars that has sufficient flexibilty and low enough cost to be utilized by a wide swath of field-going glaciologists. These pages focus on outlining suggestions for building your own version of MAPPERR. For more information on the architecture of a multi-frequency joint radar-radiometer, we refer you to the following publications:
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1 - MAPPERR Core Hardware
Minimum Required Hardware
The core components of MAPPERR are an Ettus X310 software-defined radio (SDR), an external host computer, and two antennas (one for transmitting and one for receiving). We use these log-periodic dipole array antennas, as well as homemade resistively loaded dipoles, depending on our desired center frequency. For our host computer, we typically use a laptop running Ubuntu.
MAPPERR can be operated in a basic configuration by connecting the antennas as shown in the diagram below and utilizing the default_x310.yaml configuration file with ORCA.
Interfacing with the X310
The Ettus X310 can connect to a host computer via either 1 Gb or 10 Gb ethernet. When connected via 1 Gb ethernet, the maximum radar sample rate that does not produce significant communications errors between the host computer and SDR is 25 MHz. When using 10 Gb ethernet, sample rates of up to 100 MHz are possible. To achieve the maximum possible sample rate (200 MHz), dual 10 Gb ethernet connection is needed.
Communicating with the SDR over ethernet requires network settings on the host computer to be set appropriately. See this guide and this guide from Ettus for more information. A startup script is available in ORCA that can be modified be each user. You can check that you are connected correctly to the X310 by pinging its IP address (typically 192.168.10.2 for a 1 Gb ethernet connection and 192.168.40.2 for a 10 Gb connection), or running uhd_find_devices and uhd_usrp_probe from a terminal.
UHD Version
Currently, ORCA has only been tested with an X310/MAPPERR when running and using UHD 3.15. In principle, upgrades to future UHD versions should be possible, however, we have previously run into some issues when upgrading.
2 - MAPPERR Antennas
Antennas are an important part of any radar system, and especially a multi-frequency system like MAPPERR. In a full multi-frequency active-passive configuration, we envision MAPPERR having active radar channels centered at 2, 22, 330, and 1000 MHz, along with passive radiometer channels at 300 and 1000 MHz. We use these log-periodic dipole array antennas to cover the 300 MHz and above bands. To cover the 2 and 22 MHz channels, we utilize homemade resistively loaded dipoles, each tuned to our desired center frequency.
Resistively Loaded Dipole Construction
Resistively loaded dipoles are built based on the Wu-King resistive loading method (Wu and King, 1965). We use #14 Flex-Weave^TM^ wire from Davis RF to construct our dipoles. Resistors should be rated for the appropriate peak and average power.
3 - Towing MAPPERR
Details about towing the MAPPERR system
Inner Tube Sled Design
Crossbar Sled Design