• INTERFERENCE MITIGATION OF ADJACENT RADIO FREQUENCY SIGNALS ON A FLEXIBLE SOFTWARE-DEFINED RADIO TESTBED PLATFORM

      Gonzalez, Virgilio; Elahi, Mirza M.; Sandoval, Jose C.; Corral, Pabel; Yasuda, Susumu; Univ Texas, Computational Science Program; Univ Texas, Dept Electrical and Computer Engineering; White Sands Missile Range, U.S. Army Test and Evaluation Command (International Foundation for Telemetering, 2019-10)
      The radio frequency (RF) spectrum is crowded with users and adjacent frequency users are facing an increase in interference from each other. The spectrum governing body Federal Communications Commission (FCC) has the difficult task of allocating spectral bands for new users for mobile devices using 4G LTE technology. Telemetry (TM) is affected by the adjacent band 4G LTE users in terms of signal degradation. To minimize the interference between adjacent frequency users, several methods can be used. A common but inefficient method separates adjacent band frequencies using guard bands which leaves a big portion of the spectrum unused. Alternatively, adjacent RF signals can be separated using digital filtering techniques with the signal of interest being unharmed and reducing the signal power of the interfering signal. A digital filtering technique includes bandpass filter (BPF) rejection, which has the ability to filter out adjacent interfering signals. This is accomplished by designing bandpass digital filters where the passband and stopband frequencies are adjusted to achieve maximum signal power and reject the interfering signal by reducing its power. A flexible software-defined radio testbed is set up to experiment and analyze this scenario with ease and effective measures.
    • Testing the Reliability and Flexibility of Digitizers adapting the RF/IF signals over IP applications using a testbed Platform.

      Gonzalez, Virgilio; Sandoval, Jose Carlos; Elahi, Mirza; Corral, Pabel; Yasuda, Susumu; Univ Texas, Dept Electrical and Computer Engineering; White Sands Missile Range, U.S. Army Test and Evaluation Command (International Foundation for Telemetering, 2019-10)
      Many disadvantages from physical limitations in RF Telemetry can now be eliminated using RF over IP Networks. Digitizers mitigate the problem of signal degradation that RF has due to physical restrictions and provide reliability and flexibility to the signal. The digitizers are also able to preserve both frequency and timing characteristics, and then accurately reconstructing the original Telemetry signals to enable processing, recording or retransmission at another location. The digitizers along with the software-defined radios forms a flexible testbed platform which enables us to simulate both communication systems to qualify and quantify their behavior, while studying the interference between systems. In addition, quantization of noise is a critical parameter to determine the bit error rate in the testbed. Digitizers can be configured at a certain bandwidth and additional gain, in order to make this layer almost a transparent transmission.