Editing Software-defined radio (section)

=== SpeakEasy phase I ===
From 1990 to 1995, the goal of the [[SpeakEasy]] program was to demonstrate a radio for the [[U.S. Air Force]] tactical ground air control party that could operate from 2 [[megahertz|MHz]] to 2 [[gigahertz|GHz]], and thus could interoperate with ground force radios (frequency-agile [[VHF]], [[frequency modulation|FM]], and [[SINCGARS]]), Air Force radios (VHF [[Amplitude modulation|AM]]), Naval Radios (VHF [[Amplitude modulation|AM]] and [[high frequency|HF]] [[single-sideband modulation|SSB]] [[teleprinter]]s) and [[communications satellite|satellites]] ([[microwave]] [[quadrature amplitude modulation|QAM]]).  Some particular goals were to provide a new signal format in two weeks from a standing start, and demonstrate a radio into which multiple contractors could plug parts and software.{{fact|date=August 2022}}

The project was demonstrated at [[Transformation of the United States Army#Force XXI|TF-XXI Advanced Warfighting Exercise]], and demonstrated all of these goals in a non-production radio. There was some discontent with failure of these early software radios to adequately filter out of band emissions, to employ more than the simplest of interoperable modes of the existing radios, and to lose connectivity or crash unexpectedly. Its [[cryptography|cryptographic]] processor could not change context fast enough to keep several radio conversations on the air at once. Its software architecture, though practical enough, bore no resemblance to any other. The SpeakEasy architecture was refined at the MMITS Forum between 1996 and 1999 and inspired the DoD integrated process team (IPT) for programmable modular communications systems (PMCS) to proceed with what became the Joint Tactical Radio System (JTRS).{{fact|date=August 2022}}

The basic arrangement of the radio [[receiver (radio)|receiver]] used an [[antenna (electronics)|antenna]] feeding an [[amplifier]] and down-converter (see [[Frequency mixer]]) feeding an [[automatic gain control]], which fed an [[analog-to-digital converter]] that was on a computer [[VMEbus]] with a lot of [[digital signal processor]]s ([[Texas Instruments]] C40s). The transmitter had [[digital-to-analog converter]]s on the [[PCI bus]] feeding an up converter (mixer) that led to a power amplifier and antenna. The very wide frequency range was divided into a few sub-bands with different analog radio technologies feeding the same analog to digital converters. This has since become a standard design scheme for wideband software radios.{{fact|date=August 2022}}