From f3ca0f16e693370e76c9859ba33b12f063282691 Mon Sep 17 00:00:00 2001
From: J RB <jon.roadleybattin@gmail.com>
Date: Wed, 3 Nov 2021 21:03:28 +0000
Subject: [PATCH] updated Z0 to accepted value, update ZTEM10 <-> a calc/synth
 as per #9146

---
 pcb_calculator/transline/rectwaveguide.cpp | 35 ++++++++++------------
 pcb_calculator/transline/units.h           |  5 +++-
 2 files changed, 20 insertions(+), 20 deletions(-)

diff --git a/pcb_calculator/transline/rectwaveguide.cpp b/pcb_calculator/transline/rectwaveguide.cpp
index b7b8a7001f..e7b26082e8 100644
--- a/pcb_calculator/transline/rectwaveguide.cpp
+++ b/pcb_calculator/transline/rectwaveguide.cpp
@@ -238,6 +238,7 @@ void RECTWAVEGUIDE::get_rectwaveguide_phys()
 
 /*
  * analyze - analysis function
+ * source: https://empossible.net/wp-content/uploads/2018/03/Lecture-5c-Rectangular-waveguide.pdf
  */
 void RECTWAVEGUIDE::calcAnalyze()
 {
@@ -252,9 +253,8 @@ void RECTWAVEGUIDE::calcAnalyze()
 
         // Z0 definition using fictive voltages and currents
         m_parameters[Z0_PRM] =
-                2.0 * ZF0 * sqrt( m_parameters[MUR_PRM] / m_parameters[EPSILONR_PRM] )
-                * ( m_parameters[PHYS_B_PRM] / m_parameters[PHYS_A_PRM] )
-                / sqrt( 1.0 - pow( ( fc( 1, 0 ) / m_parameters[FREQUENCY_PRM] ), 2.0 ) );
+            ZF0 * sqrt( m_parameters[MUR_PRM] / m_parameters[EPSILONR_PRM] )
+            / sqrt( 1.0 - pow( ( fc( 1, 0 ) / m_parameters[FREQUENCY_PRM] ), 2.0 ) );
 
         /* calculate electrical angle */
         lambda_g = 2.0 * M_PI / sqrt( k_square - kc_square( 1, 0 ) );
@@ -278,26 +278,23 @@ void RECTWAVEGUIDE::calcAnalyze()
 
 /*
  * synthesize - synthesis function
+ * source: re-arrangment of calcAnalyze equation
+ * TE10 (via fc(1,0) ) results in the b term not influencing the result, as long as 
+ * 1) fc > f
+ * 2) a > b
  */
 void RECTWAVEGUIDE::calcSynthesize()
 {
     double lambda_g, k_square, beta;
-
-    if( isSelected( PHYS_B_PRM ) )
-    {
-        /* solve for b */
-        m_parameters[PHYS_B_PRM] =
-                m_parameters[Z0_PRM] * m_parameters[PHYS_A_PRM]
-                * sqrt( 1.0 - pow( fc( 1, 0 ) / m_parameters[FREQUENCY_PRM], 2.0 ) )
-                / ( 2.0 * ZF0 * sqrt( m_parameters[MUR_PRM] / m_parameters[EPSILONR_PRM] ) );
-    }
-    else if( isSelected( PHYS_A_PRM ) )
-    {
-        /* solve for a */
-        m_parameters[PHYS_A_PRM] =
-                sqrt( pow( 2.0 * ZF0 * m_parameters[PHYS_B_PRM] / m_parameters[Z0_PRM], 2.0 )
-                        + pow( C0 / ( 2.0 * m_parameters[FREQUENCY_PRM] ), 2.0 ) );
-    }
+    /* solve for a */
+    m_parameters[PHYS_A_PRM] =
+        C0
+        / ( sqrt( ( m_parameters[MUR_PRM] * m_parameters[EPSILONR_PRM] ) ) * 2
+        * m_parameters[FREQUENCY_PRM] * sqrt( 1
+            - pow( ( ZF0 * sqrt( m_parameters[MUR_PRM]
+                / m_parameters[EPSILONR_PRM] ) )
+                / m_parameters[Z0_PRM]
+                ,2.0 ) ) );
 
     k_square                   = kval_square();
     beta                       = sqrt( k_square - kc_square( 1, 0 ) );
diff --git a/pcb_calculator/transline/units.h b/pcb_calculator/transline/units.h
index d604d5448c..542a294700 100644
--- a/pcb_calculator/transline/units.h
+++ b/pcb_calculator/transline/units.h
@@ -59,6 +59,9 @@ inline double atanh( double x )
 
 #define MU0  12.566370614e-7          // magnetic constant
 #define C0   299792458.0              // speed of light in vacuum
-#define ZF0  376.73031346958504364963 // wave resistance in vacuum
+#define ZF0  376.730313668           // wave resistance in vacuum
+
+// ZF0 value update:
+// https://physics.nist.gov/cgi-bin/cuu/Value?z0
 
 #endif /* __UNITS_H */