• DESIGN OF A DIGITAL VOICE ENCODER CIRCUIT

      Olyniec, Lee; Edwards Air Force Base (International Foundation for Telemetering, 1995-11)
      This paper describes the design and characteristics of a digital voice encoding circuit that uses the continuously variable slope delta (CVSD) modulation/demodulation method. With digital voice encoding, the audio signal can be placed into the pulse code modulation (PCM) data stream. Some methods of digitizing voice can require a large amount of bandwidth. Using the CVSD method, an acceptable quality of audio signal is obtained with a minimum of bandwidth. Presently, there is a CVSD microchip commercially available; however, this paper will describe the design of a circuit based on individual components that apply the CVSD method. With the advances in data acquisition technology, increased bit rates, and introduction of a corresponding MIL-STD, CVSD modulated voice will become more utilized in the flight test programs and a good knowledge of CVSD will become increasingly important. This paper will present CVSD theory, supported by graphical investigations of a working circuit under different conditions. Finally, several subjects for further study into CVSD will be addressed.
    • VME Based Ground Stations at Mcdonnell Douglas Aerospace Flight Test

      Taylor, Bruce A.; McDonnell Douglas Aerospace (International Foundation for Telemetering, 1995-11)
      The ability to dynamically configure our ground stations to support a wide array of fighter/attack aircraft programs has lead McDonnell Douglas Aerospace (MDA) to seek alternatives to commercially available ground stations. Cost effectiveness and fast response time to these widely varying needs is paramount to staying competitive in today's current defense environment. VME (Versa Modular European) architecture has provided a platform that fulfills these requirements while requiring a minimum of in house designs which can be expensive and time consuming to implement. MDA is now in its third generation of VME based ground systems. These systems are highly extensible due to their reliance on software and programmable hardware systems and are inexpensive due to their use of commercial grade VME cards. This paper describes the current generation TM/Quicklook Ground Station and the Data Editor (Preprocessor) Station and it also provides a perspective of how the designers solved some common problems associated with VME architecture. These stations are now in use at MDA test sights in St. Louis, Patuxent River NAWC, Edwards AFB, and Eglin AFB.