iqbal.c File Reference

IQ balance utils implementation. More...

Data Structures
struct	_iqbal_estimate_state
	Cache for _osmo_iqbal_estimate when doing lots of calls. More...
struct	_iqbal_state
	Internal state structure for the IQ balance optimization algorithm. More...

Functions
void	osmo_iqbal_fix (float complex *out, float complex *in, unsigned int len, float mag, float phase)
	Apply IQ balance correction to a given complex buffer. More...
struct osmo_cxvec *	osmo_iqbal_cxvec_fix (const struct osmo_cxvec *in, float mag, float phase, struct osmo_cxvec *out)
	Apply IQ balance correction to a given complex vector. More...
static void	_osmo_iqbal_estimate_release (struct _iqbal_estimate_state *state)
	Release a cache object created by _osmo_iqbal_estimate.
static float	_osmo_iqbal_estimate (const float complex *data, int fft_size, int fft_count, struct _iqbal_estimate_state **state_p)
	Objectively estimate IQ balance in a given complex buffer. More...
float	osmo_iqbal_estimate (const float complex *data, int fft_size, int fft_count)
	Objectively estimate IQ balance in a given complex buffer. More...
float	osmo_iqbal_cxvec_estimate (const struct osmo_cxvec *sig, int fft_size, int fft_count)
	Objectively estimate IQ balance in a given complex vector. More...
static float	_iqbal_objfn_value (struct _iqbal_state *state, float x[2])
	Optimization objective function - Value. More...
static void	_iqbal_objfn_gradient (struct _iqbal_state *state, float x[2], float v, float grad[2])
	Optimization objective function - Gradient estimation. More...
static float	_iqbal_objfn_val_gradient (struct _iqbal_state *state, float x[2], float grad[2])
	Optimization objective function - Value & Gradient estimation. More...
int	osmo_iqbal_cxvec_optimize (const struct osmo_cxvec *sig, float *mag, float *phase, const struct osmo_iqbal_opts *opts)
	Finds the best IQ balance correction parameters for a given signal. More...

Variables
const struct osmo_iqbal_opts	osmo_iqbal_default_opts
	Default values for the optimization algorithm. More...

Detailed Description

IQ balance utils implementation.

The actual algorithm used for estimation of the imbalance and its optimization is inspired by the IQ balancer of SDR# by Youssef Touil and described here :

http://sdrsharp.com/index.php/automatic-iq-correction-algorithm

The main differences are:

• Objective function uses complex correlation of left/right side of FFT
• Optimization based on steepest gradient with dynamic step size