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<!DOCTYPE HTML SYSTEM "html.dtd">
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<TITLE>PROGRAM CONTROL CARDS </TITLE>
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<H2>PROGRAM CONTROL CARDS</H2>
<P>The program control cards follow the structure geometry cards. They set
electrical parameters for the model, select options for the solution procedure,
and request data computation. The cards are listed below by their mnemonic
identifier with a breif description of their function:</P>
<PRE> Group I EK - extended thin-wire kernal flag
FR - fequecy specification
GN - ground parameter specification
KH - interaction approximation range
LD - structure impedance loading
Group II EX - stucture excitation card
NT - two-port network specification
TL - transmission line specification
Group III CP - coupling calculation
EN - end of data flag
GD - additional graound parameter specifications
NE - near electric field request
NH - near magnetic field request
NX - next stucture flag
PQ - wire charge density print control
PT - wire-current print control
RP - radiation pattern request
WG - write Numerical Green's Function file
XQ - execute card
</PRE>
<P> There is no fixed order for the cards. The desired parameters and options
are set first followed by requests for calculation of currents, near fields and
radiated fields. Parameters that are not set in the input data are given
default values. The one exception to this is the excitation (EX) which must be
set.</P>
<P> Computation of currents may be requested by an XQ card. RP, NE, or NH cards
cause calculation of teh currents and radiated or near fields on the first
occurrence. Subsequent RP, NE, or NH cards cause computation of fields using
the previously calculated currents. Any number of near-field and
radiation-pattern requests may be grouped together in a data deck. An exception
to this occurs when multiple frequencies are requested by a single FR card. In
this case, only a single NE or NH card and a single RP card will remain in
effect for all frequencies.</P>
<P> All parameters retain there values until changed by subsequent data cards.
Hence, after parameters have been set and currents or fields computed, selected
parameters may be changed and the calculatios repeated. For example, if a
number of different excitations are required at a single frequency, the deck
could have the form FR, EX, XQ, EX, XQ, ... If a single excitation is required
at a number of frequencies, the cards EX, FR, XQ, FR, XQ, ... could be used.
</P>
<P> When the antenna is modified and additional calculations are requested, the
order of the cards may, in some cases, affect the solutiontime since the
program will repeat only that part of the solution affected by the changed
parameters. For this reason, the user should understand the relation of the
data cards to the solution procedure. The first step in the solution is to
calculate the interaction matrix, which determines the response of the antenna
to an arbitrary excitation, and to factor this matrix in preparation for
solution of the matrix equation. This is the most time-consuming single step in
the solution procedure. The second step is to solve the matrix equation for the
currents due to a specific excitation. Finally, the near fields or radiated
fields may be computed from the currents.</P>
<P> The interaction matrix depends only on the structure geometry and the cards
in group I of the program control cards. Thus, computation and factor- ization
of the matrix is not repeated if cards beyond group I are changed. On the other
hand, antenna currents depend on both the interaction matrix and the cards in
group II, so that the currents must be recomputed whenever cards in group I or
II are changed. The near fields depend only on the structure currents while the
radiated fields depend on the currents and on the GD card, which contains
special ground parameters for the radiated-field calculation. An example of the
inplications of these rules is presented by the following two sets of data
cards:</P>
<PRE> FR, EX, NT1, LD1, XQ, LD2, XQ, NT2, LD1, XQ, LD2, XQ
FR, EX, LD1, NT1, XQ, NT2, XQ, LD2, NT1, XQ, NT2, XQ
</PRE>
<P>Calculation and factoring of the matrix would be required four times by the
first set but only twice by the second set in obtaining the same information.
</P>
<P>The program control cards are explained on the following pages. The format
of all program control cards has four integers and six floating point numbers.
The integers are contained in columns 3 through 5, 6 through 10, 11 through 15,
and 16 through 20 (each integer field stops at an integral multiple of 5
columns), and the floating point numbers are contained in fields of 10 for the
remainder of the card (i.e., from 21 through 30, 31 through 40, etc.). Integers
are right justified in their fields. The floating point numbers can be punched
either as a string of digits containing a decimal point, punched anywhere in
the field; or as a string of digits containing a decimal point and followed by
an exponent of ten in the form E +- I which multiplies the number by 10^+-I.
The integer exponent must be right justified in the field.</P>
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