• BLIND ADAPTIVE EQUALIZER FOR MULTIPATH ENVIRONMENT IN LOW ELEVATION AERONAUTICAL TELEMETRY

      Ke, Zhou; Dalong, Yang; Shunqin, Xie; Xianglu, Li; Tao, Dai; Institute of Electronic Engineering, China Academy of Engineering Physics (International Foundation for Telemetering, 2018-11)
      It has been proved that multipath and timing-varying channels usually cause significant performance degradation, especially for low elevation scenario (0o~5o) in aeronautical telemetry. Channel models for various scenarios of the whole take-off process will be described in this paper. And we will present the experimental testing results to characterize the performance of a blind adaptive constant modulus algorithm (CMA) equalizer applied for PCM-FM receiver in low elevation aeronautical telemetry scenarios, including parking scenario, taxiing scenario, take-off scenario and far-flight scenario. The test results showed that the equalizer improved the signal quality and achieved a remarkable bit error rate (BER) performance gain in the multipath fading scenarios.
    • CODE-AIDED TIMING SYNCHRONIZATION FOR MULTI-H CPM AT LOW SIGNAL-TO-NOISE RATIO

      Shunqin, Xie; Ke, Zhou; Dahai, Chen; Xianglu, Li; Institute of Electronic Engineering, China Academy of Engineering Physics (International Foundation for Telemetering, 2018-11)
      In order to solve the problem of timing synchronization at low signal-to-noise ratio(SNR) for Multi-h CPM, a code-aided early-late loop(ELL) algorithm is proposed. The algorithm is based on the iterative detection of serially concatenated Multi-h CPM with convolutional codes. The ELL timing estimator based on sequence detection is extended to the maximum-logarithmic maximum a posteriori (max-log MAP) detection. By using the information updated by iterative detection, the timing accuracy of multi-h CPM can be improved at low SNR. The simulation results show that, even when the bit signal-to-noise ratio (Eb/No) is as low as 3dB~5dB, the estimating variance of the proposed synchronization can be close to the Cramer Rao bound(MCRB) of ARTM CPM. After this timing synchronizing, the detection performance of the 10th iteration is only 0.03dB loss compared with the performance with ideal synchronization.