RASDRWin - Companion Software for RASDR

Paul Oxley Retired AT&T Microwave Engineer
David Fields
Stan Kurtz

This paper has been presented at the SARA 2014 annual meeting

ABSTRACT

An update of the RASDR project will be presented. The paper demonstrates Windows
control of the RASDR system. User-provided data specifies center frequency, bandwidth, and
some initial values used to choose optimal operational range of the Lime femtocell ship.
Additional settings govern decimation, signal processing, external reference frequency and
output options. The system uses USB2 to provide a high speed interface to the RASDR
hardware.

RASDRWin is a Windows based platform that provides the control and data analysis for the
RASDR system. It is written in C to allow portability across Windows, Linux and Mac-OS. The
portability is maintained in part by avoiding graphical user interfaces that are specific to each
platform. The use of C also provides the high speed processing necessary for data analysis at the
RASDR rates (30.72 M Samples per Second Maximum).

The control portion of RASDRWin provides the user the capability of configuring and
optimizing the LIME chip on the RASDR boards. This includes the DC calibration of the Chip
stages, minimizing second order intermodulation and optimal gain, bandwidth and sample rate
selection to meet the user’s needs.

A portion of the code also provides user control of the capability to lock the sample clock and
local oscillators to a standard reference such as a GPS receiver.

The analysis capabilities include an interface to Spectrum Labs software, a single snapshot
interface to MS-Excel for display and Fast Fourier Transform (FFT) calculation, and a capability
to produce multiple spectral line spreadsheets that are decimated to the user’s desired sample rate
and integrated over a user specified period. The decimation rates can be any power of 2 fraction
of the inherent sample rate on the board being controlled. The integration period is user variable
from 1 second to 36001 seconds. The raw sample data can also be directed to a binary file for
post collection processing. This capability also manages the amount of user’s disk space being
consumed to avoid over filling a disk.