Table Of Contents

MT Generate Synchronization Parameters (MT Generate MSK Synchronization Parameters (bit array)) (G Dataflow)

Version:
    Last Modified: February 7, 2018

    Generates synchronization parameters for MSK demodulation using a synchronization sequence directly represented by the sync bits input array. The generated synchronization parameters cluster avoids phase ambiguity at the demodulator, thus allowing recovery of the actual message bits.

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    MSK system parameters

    Parameter values defining the MSK system. Wire the MSK system parameters cluster returned by MT Generate MSK System Parameters to this cluster. Do not alter the values.

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    differential encoding enable

    A value that indicates whether the bit sequence is differentially encoded.

    Name Description
    disable

    Disables bit sequence encoding.

    enable

    Enables bit sequence encoding.

    Default: enable

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    samples per symbol

    Number of samples per symbol in the modulated output complex waveform.

    For error-free operation, the samples per symbol must be an even number. Applying Carson's rule for MSK modulation [peak frequency deviation = 0.25 × symbol rate (Hz)], the 98% MSK bandwidth is given by 0.5 × (1 + r) × symbol rate + peak frequency deviation, where 0 < r ≤ 1 is the filter parameter. To satisfy Nyquist criterion, a good guideline is given by samples per symbol = 2 × ceil(1.5 × bandwidth/symbol rate) to obtain 3× oversampling.

    Default: 16

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    sync bits

    An array of synchronization bits used to generate the MSK synchronization parameters cluster. For example, if you specify a preamble word of 1111 1111 1111 1110 for symbol synchronization, you can wire a 16-bit array with the above entries to the sync bits parameter. For reliable symbol synchronization, specify an array of length (10 × bits per symbol).

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    Note  

    To prevent false synchronization, select a bit pattern with low correlation to nonsynchronized portions of the data stream.

    Default: 0

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    error in

    Error conditions that occur before this node runs.

    The node responds to this input according to standard error behavior.

    Standard Error Behavior

    Many nodes provide an error in input and an error out output so that the node can respond to and communicate errors that occur while code is running. The value of error in specifies whether an error occurred before the node runs. Most nodes respond to values of error in in a standard, predictable way.

    error in does not contain an error error in contains an error
    If no error occurred before the node runs, the node begins execution normally.

    If no error occurs while the node runs, it returns no error. If an error does occur while the node runs, it returns that error information as error out.

    If an error occurred before the node runs, the node does not execute. Instead, it returns the error in value as error out.

    Default: No error

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    symbol rate

    The desired symbol rate, in hertz (Hz).

    Default: 1.0

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    expected sync location

    The expected location of the synchronization parameters in symbols. Set this value to -1 to search the entire waveform for the synchronization symbols.

    Default: -1

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    sync location uncertainty

    Number of symbols before or after the expected sync location where the first symbol of the sync sequence may be located. The node ignores this parameter if the expected sync location parameter is set to -1.

    Default: 10

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    sync indent

    Distance that the sync sequence is indented into the information block.

    The distance is the number of demodulated symbols preceding the sync sequence. For example, a value of 10 indicates that the output bit stream consists of 10 data symbols, followed by the sync sequence, followed by the remaining data symbols.

    Default: 0

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    MSK synchronization parameters

    Synchronization parameters to pass to the demodulation node.

    If the synchronization parameter passed to the demodulation node is left empty, the constellation of the demodulated waveform has a 90° carrier phase ambiguity for two-dimensional modulation schemes (QAM, QPSK, and higher order PSK) and a 180° carrier phase ambiguity for one-dimensional modulation schemes (PAM/ASK/BPSK).

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    expected sync location

    The expected location of the first symbol of the sync sequence.

    This value is an index to the input complex waveform. A value of -1 searches the entire input complex waveform and ignores the sync location uncertainty parameter.

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    sync sequence

    The mapped symbol pattern used to synchronize the bit stream. To prevent false synchronization, select this pattern such that there is a low probability of accidental correlation to nonsynchronized parts of the data stream. For MSK, the real portion of the mapped symbols is the frequency deviation of the symbol value, and the imaginary portion is 0. If this parameter is left empty, the signal is still demodulated.

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    sync location uncertainty

    Number of symbols before or after the expected sync location where the first symbol of the sync sequence may be located. The node ignores this parameter if the expected sync location parameter is set to -1.

    Default: 10

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    sync indent

    Distance that the sync sequence is indented into the information block.

    The distance is the number of demodulated symbols preceding the sync sequence. For example, a value of 10 indicates that the output bit stream consists of 10 data symbols, followed by the sync sequence, followed by the remaining data symbols.

    Default: 0

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    error out

    Error information.

    The node produces this output according to standard error behavior.

    Standard Error Behavior

    Many nodes provide an error in input and an error out output so that the node can respond to and communicate errors that occur while code is running. The value of error in specifies whether an error occurred before the node runs. Most nodes respond to values of error in in a standard, predictable way.

    error in does not contain an error error in contains an error
    If no error occurred before the node runs, the node begins execution normally.

    If no error occurs while the node runs, it returns no error. If an error does occur while the node runs, it returns that error information as error out.

    If an error occurred before the node runs, the node does not execute. Instead, it returns the error in value as error out.

    Where This Node Can Run:

    Desktop OS: Windows

    FPGA: Not supported

    Web Server: Not supported in VIs that run in a web application


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