pcb_calculator, STRIPLINE: fix incorrect formula for conductor loss.

pcb_calculator/transline/stripline.cpp

@@ -30,9 +30,6 @@
 #include "stripline.h"
 #include "units.h"
 
-// const to convert a attenuation / loss from log to decibel
-const double LOG2DB = 20.0 / log( 10.0 );
-
 STRIPLINE::STRIPLINE() : TRANSLINE()
 {
     m_Name = "StripLine";
@@ -41,7 +38,7 @@ STRIPLINE::STRIPLINE() : TRANSLINE()
 
 
 // -------------------------------------------------------------------
-// calculate characteristic impedance and conductor loss (in log/meter)
+// calculate characteristic impedance and conductor loss (in db/meter)
 double STRIPLINE::lineImpedance( double height, double& ac )
 {
     double ZL;
@@ -98,7 +95,7 @@ void STRIPLINE::calcAnalyze()
     m_parameters[Z0_PRM] = 2.0
                            / ( 1.0 / lineImpedance( 2.0 * a + t, ac1 )
                                    + 1.0 / lineImpedance( 2.0 * ( h - a ) - t, ac2 ) );
-    m_parameters[LOSS_CONDUCTOR_PRM]  = LOG2DB * m_parameters[PHYS_LEN_PRM] * ( ac1 + ac2 );
+    m_parameters[LOSS_CONDUCTOR_PRM]  = m_parameters[PHYS_LEN_PRM] * ( ac1 + ac2 );
     m_parameters[LOSS_DIELECTRIC_PRM] = LOG2DB * m_parameters[PHYS_LEN_PRM]
                                         * ( M_PI / C0 ) * m_parameters[FREQUENCY_PRM]
                                         * sqrt( m_parameters[EPSILONR_PRM] )

pcb_calculator/transline/units.h

@@ -61,6 +61,10 @@ inline double atanh( double x )
 #define C0   299792458.0              // speed of light in vacuum
 #define ZF0  376.730313668           // wave resistance in vacuum
 
+// const to convert a attenuation / loss from log (Neper) to decibel
+// (1 Np = 8.68589 dB)
+const double LOG2DB = 20.0 / log( 10.0 );
+
 // ZF0 value update:
 // https://physics.nist.gov/cgi-bin/cuu/Value?z0