From e45fc5d020193ea59302717bbd0666dd0508aa72 Mon Sep 17 00:00:00 2001
From: Jens Ahrensfeld <jens@jayfield.org>
Date: Wed, 15 Jun 2022 15:37:06 +0000
Subject: [PATCH] - added alternate_impl for gardner

git-svn-id: http://moon:8086/svn/software/trunk/libsrc/radio@991 b431acfa-c32f-4a4a-93f1-934dc6c82436
---
 synchronization.c | 18 +++++++++++++++---
 synchronization.h |  1 +
 2 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/synchronization.c b/synchronization.c
index 61ec962..ce37bc0 100755
--- a/synchronization.c
+++ b/synchronization.c
@@ -91,6 +91,7 @@ void LeadLagSetState(lead_lag_filter_t *pObj, radio_float_t state)
 void STRGardnerInit(str_t *pObj)
 {
 	memset(pObj->d, 0, sizeof(pObj->d));
+	pObj->alternate_impl = 0;
 }
 
 radio_float_t STRGardnerProcess(str_t *pObj, cpx_t x)
@@ -100,9 +101,20 @@ radio_float_t STRGardnerProcess(str_t *pObj, cpx_t x)
 
 	pD = pObj->d;
 
-	t.real = (pD[1].real - x.real) * pD[0].real;
-	t.imag = (pD[1].imag - x.imag) * pD[0].imag;
-	Vd = (t.real + t.imag);
+	if (pObj->alternate_impl)
+	{
+		t.real = (x.real - pD[1].real) * pD[0].real;
+		t.imag = (x.imag - pD[1].imag) * pD[0].imag;
+
+		radio_float_t sign = (t.real*t.imag) < 0 ? -1.0 : 1.0;
+		Vd = sqrt(fabs(t.real) * fabs(t.imag)) * sign;
+	}
+	else
+	{
+		t.real = (pD[1].real - x.real) * pD[0].real;
+		t.imag = (pD[1].imag - x.imag) * pD[0].imag;
+		Vd = (t.real + t.imag);
+	}
 
 	// Adjust delay line
 	pD[1] = pD[0];
diff --git a/synchronization.h b/synchronization.h
index 0cc1655..34d8b6d 100755
--- a/synchronization.h
+++ b/synchronization.h
@@ -32,6 +32,7 @@ typedef struct _lead_lag_coeff_t
 typedef struct _str_t
 {
 	cpx_t d[2];
+	int alternate_impl;
 
 } str_t;