From af17abd0538c6db47c9035b2923a2b7ec675f6b6 Mon Sep 17 00:00:00 2001
From: TT <edy555@gmail.com>
Date: Sat, 10 Aug 2019 13:16:17 +0900
Subject: [PATCH] fix: sign failure on impedance calculation

---
 plot.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/plot.c b/plot.c
index 3ee50fb..b6045c5 100644
--- a/plot.c
+++ b/plot.c
@@ -571,7 +571,7 @@ gamma2imp(char *buf, int len, const float coeff[2], uint32_t frequency)
   // z = (gamma+1)/(gamma-1) * z0
   float z0 = 50;
   float d = z0 / ((1-coeff[0])*(1-coeff[0])+coeff[1]*coeff[1]);
-  float zr = ((1+coeff[0])*(1-coeff[0]) + coeff[1]*coeff[1]) * d;
+  float zr = ((1+coeff[0])*(1-coeff[0]) - coeff[1]*coeff[1]) * d;
   float zi = 2*coeff[1] * d;
   int n;