Receives a sequence of data bits, performs PAM modulation, and returns the modulated complex baseband waveform in the output complex waveform parameter.
PAM modulation involves mapping the input bit stream to PAM symbols (as specified by the PAM symbol map), interpolating by zero-insertion, and applying the pulse-shaping filter to the interpolated I/Q data.
If you use the finite impulse response pulse-shaping filters in modulation nodes, it may lead to the apparent loss of bits caused by filter delay. Refer to Filter Delay in the Details for more information about this effect. Set the flush buffers? parameter to TRUE to offset the effects of filter delay in single-shot operations or in the last iteration of continuous operations.
Parameter values defining the PAM system. Wire the PAM system parameters cluster of MT Generate PAM System Parameters (M) or MT Generate PAM System Parameters (map) to this cluster. Do not alter the values.
An ordered array that maps each symbol to its desired level. The number of PAM levels in the array is 2^{ N }, where N is the number of bits per symbol. The vector length for the symbols farthest from the origin is 1.
The desired symbol rate, in hertz (Hz). This value must be positive.
Default: 1.00
An ordered array containing the desired sample-spaced coefficients for the pulse-shaping filter. Wire the pulse shaping filter coefficients parameter of MT Generate Filter Coefficients to this parameter. When generating the filter coefficients, ensure that the value of the pulse shaping samples per symbol parameter of MT Generate Filter Coefficients is equal to the value of the samples per symbol element of the PAM system parameters cluster, which is passed to this node.
When you configure reset? to TRUE, there is a transient response of half the filter length at the start of the modulated signal, and the output data is shortened by approximately half the filter length. When you configure reset? to FALSE, this node uses data from the previous iteration to eliminate the transient.
Error conditions that occur before this node runs. The node responds to this input according to standard error behavior.
Default: no error
A Boolean that determines whether the node continues modulating using the previous iteration states. The node resets on the first call and when you configure reset? to TRUE. You must configure reset? to TRUE the first time this node is called and whenever you want to restart the modulator.
Default: TRUE
A Boolean that determines whether samples are forced out from the modulated waveform that are affected by the FIR pulse-shaping filter delay. Set this parameter to TRUE during single-shot operations and during the last iteration of continuous operations.
TRUE | Destroys the internal states of the algorithms such that you cannot perform continuous processing on the signal during subsequent iterations. If flush buffers? is set to TRUE, you must set reset? to TRUE on the subsequent iteration. |
FALSE | Stores the internal states of the algorithms so that you can perform continuous processing on the signal during subsequent iterations. |
Default: FALSE
The modulated complex baseband waveform data.
Time of the first value in the Y array.
Time interval between data values in the Y array.
Default: 1.0
The complex-valued signal-only baseband modulated waveform. The real and imaginary parts of this complex data array correspond to the in-phase (I) and quadrature-phase (Q) data, respectively.
The array of mapped symbols before pulse shaping is applied. The array represents the complex value of each mapped symbol.
where
P is the filter order
x[n] is the input signal
y[n] is the output signal
b_{i} are the filter coefficients
The initial state for all samples in an FIR filter is 0. The filter output until the first input sample reaches the middle tap (the first causal sample) is called the transient response, or filter delay. For an FIR filter that has N taps, the delay is (N-1)/2 samples. This relationship is illustrated in the following figure, where a sine wave is filtered by an FIR filter with 50 taps.
In single-shot operations for modulators and demodulators, the filter delay is truncated before the signal is generated because these samples are not valid. Some samples at the end of the block do not appear at the modulator or demodulator output, and hence appear to have been lost.
Where This Node Can Run:
Desktop OS: Windows
FPGA: Not supported