nec_ground.cpp

矩量法仿真电磁辐射和散射的源代码（c++）

/*
	Copyright (C) 2004  Timothy C.A. Molteno
	
	This program is free software; you can redistribute it and/or modify
	it under the terms of the GNU General Public License as published by
	the Free Software Foundation; either version 2 of the License, or
	(at your option) any later version.
	
	This program is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
	GNU General Public License for more details.
	
	You should have received a copy of the GNU General Public License
	along with this program; if not, write to the Free Software
	Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*/
#include "math_util.h"
#include "nec_exception.h"
/*
	\section{NEC Ground Specification}
	
	\subsection{the GN Card}
	
	The GN card specifies the relative dielectric constant and conductivity of ground in the vicinity of the antenna. 
	In addition, a second set of ground parameters for a second medium can be specified,
	or a radial wire ground screen can be modeled using a reflection coefficient approximation.
	
	The parameters of the second medium can also be specified on another data card whose mnemonic is GD.
	With the GD card, the parameters of the second medium can be varied and only the radiated fields
	need to be recalculated.
	Furthermore, if a radial wire ground screen has been specified on the GN card,
	the GD card is the only way to include a second medium.
	See Section~\ref{sec_card_gd} for details.
	
	\subsection{"gd" card: ground representation}
	\label{sec_card_gd}
	
	To specify the ground parameters of a second medium which is not in the immediate vicinity of the antenna.
	This card may only be used if a GN card has also been used.
	It does not affect the fields of surface patches.
	
	<ground type=finite>
		<dielectric_constant = 80/>
		<conductivity = 4/>
		<radial-wire>
			<count=12>
			<length=15 unit=cm>
			<
		</radial-wire>
	</ground>
	
*/
#include "nec_ground.h"
#include "nec_output.h"
#include "misc.h" // for stop() function

/*
	Parse a GN card. The input parameters here are the fields of the
	GN card.
		
GN		NEAR GROUND, GROUND SCREEN, ADDED GROUND
	I1- -1=SET FREE SPACE (A), 0=REFL COEFF, 1=IDEAL (B), 2-SOMMERFIELD
	I2- (A) BLANK), NO WIRES IN GND SCREEN (C), 0= NO WIRES (D)
	I3- BLANK
	I4- BLANK
	F1- (A,B) BLANK, DIELECTRIC OF NEAR GROUND
	F2- (A,B) BLANK, CONDUCTIVITY OF NEAR GROUND
	F3- (A,B) BLANK, (C) RADIUS OF SCREEN, (D) DIELECTRIC 2ND MEDIUM
	F4- (A,B) BLANK, (C) RADII SCREEN WIRES, (D) CONDUCT. 2ND MEDIUM
	F5- (A,B) BLANK, (C) BLANK, (D) DIST TO 2ND MEDIUM, SEE RP
	F6- (A,B) BLANK, (C) BLANK, (D) HEIGHT 2ND MEDIUM (AS IN GD)
*/
void nec_ground::parse_gn(int itmp1, int itmp2,
	nec_float tmp1, nec_float tmp2,
	nec_float tmp3, nec_float tmp4,
	nec_float tmp5, nec_float tmp6
	)
{
	// iperf = -1 - nullifies ground parameters previously used and sets free- space condition.
	// The remainder of the card is left blank in this case. 
	
	if ( itmp1 == -1 ) // nullify previous ground conditions.
	{
		ksymp=1;
		radial_wire_count=0;
		iperf=0;
		return;
	}

	iperf = itmp1;
	ASSERT(iperf >= 0);
	
	radial_wire_count = itmp2;
	ksymp = 2;
	epsr = tmp1;
	sig = tmp2;

	if (radial_wire_count != 0)
	{
		if ( iperf == 2)
		{
			throw new nec_exception("RADIAL WIRE G.S. APPROXIMATION MAY NOT BE USED WITH SOMMERFELD GROUND OPTION");
		}
	
		radial_wire_length= tmp3;
		radial_wire_radius= tmp4;
		return;
	}

	setup_cliff(tmp3,tmp4,tmp5,tmp6);
}

/*
	Setup a cliff (two medium ground)
*/
void nec_ground::setup_cliff(nec_float in_eprs2,
	nec_float in_sig2,
	nec_float clt, nec_float cht)
{
	cliff_edge_distance = clt;
	cliff_height = cht;
	epsr2 = in_eprs2;
	sig2 = in_sig2;
}

using namespace std;

nec_complex nec_ground::get_zrati2(nec_float wavelength)
{
	return sqrt(1.0 / nec_complex(epsr2,-sig2 * wavelength * 59.96));
}