File measure_core.h¶

FileList > inc > measure > measure_core.h

Measure module — shared result structs and module-level helpers. More...

#include "clib_common.h"

Classes¶

Type	Name
struct	imd_meas_t Two-tone intermodulation result (IMD2/IMD3/TOI).
struct	npr_meas_t Noise Power Ratio (notched-noise loading) result.
struct	time_stats_t Time-domain capture statistics (AC-coupled crest/PAPR).
struct	tone_meas_t Single-tone dynamic-measurement bag.

Public Functions¶

Type	Name
double	dp_coherent_freq (double fs, double f_target, size_t N) Nearest leakage-free coherent test frequency.
size_t	measure_min_samples (double fs, double target_rbw, size_t bits, double dynamic_range_db, int complex_input) Samples needed to reach a target resolution bandwidth.
double	measure_proc_gain (size_t nfft) FFT processing gain in dB: 10log10(nfft / 2).*
size_t	measure_rec_nfft (size_t n, size_t pad) Recommended zero-padded transform length: next_pow2(n max(pad,1)).*

Public Static Functions¶

Type	Name
double	measure_dr_from_bits (size_t bits) Default dynamic-range target (dB) implied by an ADC bit depth.
double	measure_resolve_dr (double dynamic_range_db, size_t bits) Resolve the dynamic-range target from the override/bits/default chain.

Macros¶

Type	Name
define	MEASURE_DR_DEFAULT_DB `120.0`
define	MEASURE_DR_MARGIN_DB `12.0`
define	MEASURE_PAD `2u`
define	MEASURE_SPUR_SIDELOBES `1.0`

Detailed Description¶

The doppler.measure objects (ToneMeasure, …) each own a window + FFT and analyse a time-domain capture, returning one of these plain-C result bags by out-parameter. Every spectral metric integrates a component's power over its window MAIN LOBE (IEEE Std 1241) rather than reading a single peak bin, so the reading is independent of where the tone falls between FFT bins.

Public Functions Documentation¶

function dp_coherent_freq¶

Nearest leakage-free coherent test frequency.

double dp_coherent_freq (
    double fs,
    double f_target,
    size_t N
)

Snaps f_target to J * fs / N where J is the nearest integer cycle count that is coprime with N — an integer number of cycles in the capture (no leakage) with J coprime to N (so quantisation-noise correlation is minimised).

Returns:

The coherent frequency (Hz), or 0 on bad args.

function measure_min_samples¶

Samples needed to reach a target resolution bandwidth.

size_t measure_min_samples (
    double fs,
    double target_rbw,
    size_t bits,
    double dynamic_range_db,
    int complex_input
)

Plans a capture for the same auto-Kaiser window the measurement objects use: the dynamic-range target (from dynamic_range_db, else bits) selects the Kaiser beta, whose ENBW (measured via kaiser_enbw) sets the bins-per-RBW. RBW = ENBW * fs / n, so n = ceil(ENBW * fs / target_rbw).

Parameters:

fs Sample rate (Hz, > 0).
target_rbw Desired resolution bandwidth (Hz). When <= 0 it defaults to span/1000, where span = fs/2 for real captures and fs for complex (complex_input).
bits ADC depth: sets the dynamic-range target when no explicit override is given.
dynamic_range_db Explicit dynamic-range target (dB); used when > 0.
complex_input Non-zero if the capture is complex (span = fs).

Returns:

Required capture length, or 0 on bad args.

function measure_proc_gain¶

FFT processing gain in dB: 10*log10(nfft / 2).

double measure_proc_gain (
    size_t nfft
)

function measure_rec_nfft¶

Recommended zero-padded transform length: next_pow2(n * max(pad,1)).

size_t measure_rec_nfft (
    size_t n,
    size_t pad
)

Public Static Functions Documentation¶

function measure_dr_from_bits¶

Default dynamic-range target (dB) implied by an ADC bit depth.

static inline double measure_dr_from_bits (
    size_t bits
)

Ideal quantisation SNR is 6.02*bits + 1.76 dB; add MEASURE_DR_MARGIN_DB of headroom so the window's first sidelobe sits below the converter's own floor.

Parameters:

bits ADC depth in bits (> 0).

Returns:

Dynamic-range / sidelobe-attenuation target in dB.

function measure_resolve_dr¶

Resolve the dynamic-range target from the override/bits/default chain.

static inline double measure_resolve_dr (
    double dynamic_range_db,
    size_t bits
)

Parameters:

dynamic_range_db Explicit target (dB); used when > 0.
bits ADC depth; used (via measure_dr_from_bits) when the override is unset and bits > 0.

Returns:

Dynamic-range / sidelobe-attenuation target in dB.

Macro Definition Documentation¶

define MEASURE_DR_DEFAULT_DB¶

#define MEASURE_DR_DEFAULT_DB `120.0`

define MEASURE_DR_MARGIN_DB¶

#define MEASURE_DR_MARGIN_DB `12.0`

define MEASURE_PAD¶

#define MEASURE_PAD `2u`

define MEASURE_SPUR_SIDELOBES¶

#define MEASURE_SPUR_SIDELOBES `1.0`

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