• PERFORMANCE OF FQPSK TRANSCEIVERS IN A COMPLEX REAL-LIFE INTERFERENCE ENVIRONMENT

      Haghdad, Mehdi; Feher, Kamilo; University of California; Digcom Inc. (International Foundation for Telemetering, 2000-10)
      The Bit Error Rate (BER) performance of FQPSK modulated signals in the presence of the Co-Channel Interference (CCI) and Additive White Gaussian Noise (AWGN) is evaluated and improved. A Non- Linearly Amplified (NLA) FQPSK modulated signal with the data rate of 1Mb/s and carrier frequency of 70 MHz is interfered with a sinusoidal signal at different frequencies. As the relative distance of the center frequency of the Co-channel interference (CCI) changes, different BER are obtained. The effect of the CCI decreases as the CCI center frequency moves away from the center of the modulated signal. In order to improve the BER in the presence of the CCI, a hard limited filter is added at the receiver input. The hard limited filter has a different amplification factor for different signal strength. As a result, the amplification factor for the CCI, which is normally a weaker signal, is smaller than the actual signal. This means that the signal is amplified more than the interference and as a result the CCI is suppressed and the BER rate improves. The results of both simulations and measurements are obtained for different CCI center frequencies, before and after the improvements.
    • SHOCK & VIBRATION TESTING OF AN AIRBORNE INSTRUMENTATION DIGITAL RECORDER

      Smedley, Mark; Simpson, Gary; Naval Air Warfare Center Aircraft Division; Metrum-Datatape Inc. (International Foundation for Telemetering, 2000-10)
      Shock and vibration testing was performed on the Metrum-Datatape Inc. 32HE recorder to determine its viability as an airborne instrumentation recorder. A secondary goal of the testing was to characterize the recorder operational shock and vibration envelope. Both flight testing and laboratory environmental testing of the recorder was performed to make these determinations. This paper addresses the laboratory portion of the shock and vibration testing and addresses the test methodology and rationale, test set-up, results, challenges, and lessons learned.