Design 1
Jack Browne, Technical Director
during the development of the
United States Army’s Joint
SOFTWARE-DEFINED RADIOS (SDRs) can Tactical Radio System (JTRS), change function by means of programming. Already still projected to be the single a staple of many military, Homeland Security, and largest market for SDRs. The
First Responder applications, the technology is also open-architecture SCA framework 2. The Signature High
finding its way into commercial communications aims for the scalability and Performance Signal Analyzer
can be programmed with MAT-
systems. Of course, in front of an SDR’s advanced reusability of SDR software and LAB mathematical software for
digital-signal-processing (DSP) hardware sits a hardware across joint services. analysis of advanced SDR
broadband radio front end that must accommodate Because of the wide bandwidth waveforms.
a wide range of waveforms and modulation for- of an SDR’s front end, the test
mats. And testing that front end is no simple matter. equipment for evaluating that front end must be able
Fortunately, modern test instruments nominally to emulate the RF operations of the SDR front end.
developed to emulate the exotic waveforms found The MG3700A Vector Signal Generator (Fig. 1) and
in cellular networks can be adapted quite nicely to the Signature High Performance Signal Analyzer
the test needs of SDR RF front ends. (Fig. 2) from Anritsu Co. ( www.us.anritsu.com) are
A typical SDR developed for tactical radio appli- two instruments that team to provide most of the RF
cations features an extended frequency range for measurements needed for an SDR’s front end.
compatibility with legacy HF, VHF, The MG3700A covers 250 kHz
and UHF tactical radios, often as to 3 GHz in its standard configura-
wide as 2 MHz to 2 GHz. The tion, with an option to extend the
software portion of an SDR, which frequency range to 6 GHz. It has
is defined by the Software an internal in-phase/quadrature
Communications Architecture (I/Q) modulator for generating mod-
(SCA), defines the radio’s opera- 1. The MG3700A Vector Signal ulation formats as wide as 150
tion from the physical layer (PHY) Generator provides the fre- MHz as well as an internal 160-
quency range and instanta-
through the higher-level protocol neous bandwidth needed for MSamples/s arbitrary waveform
layers. The SCA was promoted generating SDR waveforms. generator to assist in the creation
of advanced modulation waveforms. With dual waveform memory locations, the MG3700A can be generate a pair of simultaneous waveforms to emulate radio performance with an interferer or jamming source.
Generating test signals is one-half of the SDR test challenge; analyzing them is the other part.
The Signature High Performance
Signal Analyzer, which can substitute for an SDR receiver’s RF front end, ranges from 100 Hz to 8 GHz with phase noise of –116 dBc/Hz offset 10 kHz from a 1-GHz carrier. With a wide dynamic range established by its third-order intercept point of +22 dBm and displayed average noise level (DANL) of –167 dBm using 14-b analog-to-digital converters (ADCs), the analyzer can capture and display even the widest-dynamic-range SDR signals.
Editor’s Note: This article is based on an application note by Anritsu Co., “Understanding SDRs and their RF Test Requirements,” and available at their website at www.us.anritsu.com.
References:
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