File channel_core.h¶

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GPS-style tracking channel — Costas carrier loop + DLL code loop. More...

• #include "clib_common.h"
• #include "dp_state.h"
• #include "costas/costas_core.h"
• #include "dll/dll_core.h"
• #include "jm_perf.h"
• #include <complex.h>
• #include "lo/lo_core.h"
• #include "loop_filter/loop_filter_core.h"

Classes¶

Public Functions¶

Macros¶

Detailed Description¶

A complete tracking channel for a continuous DSSS-BPSK signal: it composes a costas_state_t carrier loop and a dll_state_t code loop on a single shared per-sample integrate-and-dump. Per sample it wipes the carrier (costas_wipeoff, integer NCO) and feeds the de-rotated sample to the DLL's early/prompt/late correlators (dll_accumulate); per code period it dumps the prompt and updates both loops — the code loop on the early/late envelopes, the carrier loop on the same prompt symbol. steps() emits one prompt per period; bits() bit-syncs the prompts into hard data bits (a data bit spans nav_period code periods).

It is seeded by acquisition (the FFT search supplies the coarse carrier frequency + code phase); the loops then track the residual. Set bn_fll > 0 for FLL-assisted carrier pull-in.

Lifecycle: channel_create -> [steps / bits / reset]* -> channel_destroy.

uint8_t code[127] = { ... };  // one code period, 0/1 chips
channel_state_t *ch = channel_create(code, 127, 8, 0.0, 0.0,
                                      0.05, 0.005, 0.0, 0.707, 0.5, 1);
float complex sym[64];
size_t k = channel_steps(ch, rx, rx_len, sym, 64);  // prompt per period
channel_destroy(ch);

Public Functions Documentation¶

function channel_bits¶

size_t channel_bits (
    channel_state_t * state,
    const float complex * x,
    size_t x_len,
    uint8_t * out,
    size_t max_out
) 

function channel_bits_max_out¶

size_t channel_bits_max_out (
    channel_state_t * state
) 

function channel_create¶

Create a tracking channel (COPIES code ).

channel_state_t * channel_create (
    const uint8_t * code,
    size_t code_len,
    size_t sps,
    double init_norm_freq,
    double init_chip,
    double bn_carrier,
    double bn_code,
    double bn_fll,
    double zeta,
    double spacing,
    size_t nav_period
) 

Returns:

Heap-allocated state, or NULL on allocation failure.

Note:

Caller must call channel_destroy() when done.

function channel_destroy¶

Destroy a tracking channel and release all memory.

void channel_destroy (
    channel_state_t * state
) 

Parameters:

• state May be NULL.

function channel_get_bit_phase¶

size_t channel_get_bit_phase (
    const channel_state_t * state
) 

function channel_get_bn_carrier¶

double channel_get_bn_carrier (
    const channel_state_t * state
) 

function channel_get_bn_code¶

double channel_get_bn_code (
    const channel_state_t * state
) 

function channel_get_code_phase¶

double channel_get_code_phase (
    const channel_state_t * state
) 

function channel_get_code_rate¶

double channel_get_code_rate (
    const channel_state_t * state
) 

function channel_get_lock_metric¶

double channel_get_lock_metric (
    const channel_state_t * state
) 

function channel_get_norm_freq¶

double channel_get_norm_freq (
    const channel_state_t * state
) 

function channel_get_state¶

void channel_get_state (
    const channel_state_t * state,
    void * blob
) 

function channel_init¶

Initialise a tracking channel in place; BORROWS code .

void channel_init (
    channel_state_t * ch,
    const uint8_t * code,
    size_t code_len,
    size_t sps,
    double init_norm_freq,
    double init_chip,
    double bn_carrier,
    double bn_code,
    double bn_fll,
    double zeta,
    double spacing,
    size_t nav_period
) 

The by-value counterpart to channel_create(): the caller retains ownership of code (it is not copied or freed). Seeds the carrier NCO at init_norm_freq and the code phase at init_chip (the acquisition estimate). The carrier loop's update period is one code period (code_len * sps samples).

Parameters:

• ch State to initialise. Must be non-NULL.
• code Spreading code (0/1 chips), one period; borrowed.
• code_len Code length (chips per period); >= 1.
• sps Samples per chip.
• init_norm_freq Seed carrier frequency, cycles/sample.
• init_chip Seed code phase, chips.
• bn_carrier Carrier loop noise bandwidth.
• bn_code Code loop noise bandwidth.
• bn_fll Carrier FLL-assist bandwidth (0 = pure PLL).
• zeta Damping factor for both loops.
• spacing DLL early/late tap offset, chips.
• nav_period Code periods per data bit (1 = one bit per period).

function channel_reset¶

Re-seed both loops to the create-time frequency/phase; keep config.

void channel_reset (
    channel_state_t * state
) 

Parameters:

• state Must be non-NULL.

function channel_set_bn_carrier¶

void channel_set_bn_carrier (
    channel_state_t * state,
    double val
) 

function channel_set_bn_code¶

void channel_set_bn_code (
    channel_state_t * state,
    double val
) 

function channel_set_norm_freq¶

void channel_set_norm_freq (
    channel_state_t * state,
    double val
) 

function channel_set_state¶

int channel_set_state (
    channel_state_t * state,
    const void * blob
) 

function channel_state_bytes¶

size_t channel_state_bytes (
    const channel_state_t * state
) 

function channel_steps¶

size_t channel_steps (
    channel_state_t * state,
    const float complex * x,
    size_t x_len,
    float complex * out,
    size_t max_out
) 

function channel_steps_max_out¶

size_t channel_steps_max_out (
    channel_state_t * state
) 

Macro Definition Documentation¶

define CHANNEL_STATE_MAGIC¶

#define CHANNEL_STATE_MAGIC `DP_FOURCC ('C','H','A','N')`

define CHANNEL_STATE_VERSION¶

#define CHANNEL_STATE_VERSION `1u`

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