File wfm_dsp.h¶

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DSSS spreading + root-raised-cosine pulse shaping (Phase B). More...

#include "clib_common.h"

Public Functions¶

Type	Name
void	wfm_dsss_spread (const float _Complex * syms, size_t n_sym, const uint8_t * code, size_t sf, float _Complex * out) Spread `n_sym` complex data symbols by a binary PN code.
void	wfm_rrc_taps (double beta, int sps, int span, float * taps) Fill `taps` with a unit-energy root-raised-cosine impulse response.

Public Static Functions¶

Type	Name
size_t	wfm_rrc_ntaps (int sps, int span) Number of taps a `wfm_rrc_taps` call produces:`2spansps + 1` .

Detailed Description¶

Two pure DSP primitives the engine/composer use to build spread-spectrum and band-limited waveforms: * wfm_dsss_spread: multiply each data symbol by a PN chip code. * wfm_rrc_taps: a unit-energy root-raised-cosine FIR (matched-filter pulse shape), applied by upsample + FIR.

Public Functions Documentation¶

function wfm_dsss_spread¶

Spread n_sym complex data symbols by a binary PN code.

void wfm_dsss_spread (
    const float _Complex * syms,
    size_t n_sym,
    const uint8_t * code,
    size_t sf,
    float _Complex * out
)

out[i*sf + j] = syms[i] * (code[j] ? -1 : +1) — each symbol is repeated across sf chips, sign-flipped per code chip. Output length is n_sym*sf. Works for BPSK (real syms) and QPSK (complex syms).

Parameters:

syms complex data symbols;
n_sym their count.
code PN chip code (0/1), length sf;
sf spreading factor.
out output chips, length n_sym * sf.

function wfm_rrc_taps¶

Fill taps with a unit-energy root-raised-cosine impulse response.

void wfm_rrc_taps (
    double beta,
    int sps,
    int span,
    float * taps
)

Length is wfm_rrc_ntaps(sps, span); the response is symmetric about the centre tap and normalised so sum(taps^2) == 1 (so cascading TX·RX gives a Nyquist raised cosine). The t = 0 and t = ±1/(4β) singularities are handled by their closed-form limits.

Parameters:

beta roll-off in [0, 1].
sps samples per symbol (>= 1).
span one-sided span in symbols (>= 1).
taps output array of length wfm_rrc_ntaps(sps, span).

Public Static Functions Documentation¶

function wfm_rrc_ntaps¶

Number of taps a wfm_rrc_taps call produces:2*span*sps + 1 .

static inline size_t wfm_rrc_ntaps (
    int sps,
    int span
)

Parameters:

sps samples per symbol (>= 1).
span one-sided filter span in symbols (>= 1).

The documentation for this class was generated from the following file native/inc/wfm/wfm_dsp.h