Receiver structure and estimation of the modulation index for tamed frequency modulated (TFM) signals

Markku Kiviranta (Corresponding Author), Aarne Mämmelä

    Research output: Contribution to journalArticleScientificpeer-review


    Tamed frequency modulation (TFM) is a spectrally efficient constant amplitude continuous phase modulation (CPM) scheme which can be simply realized by using a frequency modulator (FM). In the implementation the modulation index of TFM is calibrated to have a nominal value of 0.5, but due to temperature variations it can drift causing time varying phase jitter. In this paper we present novel algorithms and performance results to measure and control the modulation index in a coherent receiver based on the joint reduced state sequence detector (RSSD) and per-survivor processing (PSP) carrier phase estimation. The modulation index estimator measures phase transitions in the receiver and derives estimates by comparing the result to the coding rule of the TFM signal. The estimator has acquisition and tracking ability, and the current estimate can be used to replace the nominal index value. Our simulation results show that the proposed coherent receiver with the novel modulation index estimator has less than 1 dB performance degradation compared to around 4.5 dB exploiting only the PSP carrier phase estimation.
    Original languageEnglish
    Pages (from-to)61-71
    Number of pages11
    JournalPhysical Communication
    Publication statusPublished - 2014
    MoE publication typeA1 Journal article-refereed


    • continuous phase modulation
    • demodulation
    • frequency modulation
    • parameter estimation
    • viterbi alhorithm


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