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<HTML><HEAD><TITLE>Networks (NT)</TITLE></HEAD>
<BODY>
<H2><center>Networks (NT)</center></h2>
<u><b>Purpose:</u></b>
<p>To generate a two-port nonradiating, network connected between any
two segments in the structure. The characteristics of the network
are specified by its short-circuit admittance matrix elements. For
the special case of a transmission line, a separate card is provided
for convenience although the mathematical method is the same as for
networks. Refer to the TL card.
<p>
<u><b>Card:</b></u>
<pre>
_________________________________________________________________
/2| 5| 10| 15| 20| 30| 40| 50| 60| 70| 80|
/ | | | | | | | | | | |
| | | | | | | | | | | |
|NT |I1 | I2 | I3 | I4 | F1 | F2 | F3 | F4 | F5 | F6 |
| | | | | | | | | | | |
| | | | | | Y11R | Y11I | Y12R | Y12I | Y22R | Y22I |
| | | | | | | | | | | |
| | | | | | | | | | | |
| | | | | | | | | | | |
| | | | | | | | | | | |
| | | | | | | | | | | |
| The numbers along the top refer to the last column in each field |
| | | | | | | | | | | |
</PRE>
<dl>
<dt><u><b>Parameters:</u></b>
<dl>
<dt><b>Integers</b>
<dd><dt><u>(I1)</u> - Tag number of the segment to which
port one of the network
is connected. This tag number along with the number to be
given in (I2), which identifies the position of the segment
in a set of equal tag numbers, uniquely defines the segment
for port one. Blank or zero here implies that the segment
will be identified, using the absolute segment number in the
next location (12).
<p>
<dd><dt><u>(I2)</u> - Equal to m, specifies the m<sup>th</sup> segment
of the set of segments
whose tag numbers are equal to the number set by the previous
parameter. If the previous parameter is zero, the number in
(12) is the absolute segment number corresponding to end one
of the network. A minus one in this field will nullify all
previous network and transmission line connections. The
rest of the card is left blank in this case.
<p>
<dd><dt><u>(I3) & (I4)</u> - Used in exactly the same way as
(Il) & (I2) in order
to specify the segment corresponding to port two of the
network connection.
</dl>
<p>
<dl><dt><b>Floating point</b>
<br>
The six floating-point fields are used to specify the real and
imaginary parts of three short circuit admittance matrix elements
(1, 1), (1, 2), and (2, 2), respectively. The admittance
matrix is symmetric so it is unnecessary to specify element (2, 1).
<dd><u>Y11R (F1)</u> - Real part of element (1, 1) in mhos.
<dd><u>Y11I (F2)</u> - Imaginary part of element (1, 1) in mhos.
<dd><u>Y12R (F3)</u> - Real part of element (1, 2) in mhos.
<dd><u>Y12I (F4)</u> - Imaginary part of element (1, 2) in mhos.
<dd><u>Y22R (F5)</u> - Real part of element (2, 2) in mhos.
<dd><u>Y22I (F6)</u> - Imaginary part of element (2, 2) in mhos.
</dl>
</dl>
<b><u>Notes:</u></b>
<ul>
<li>Network cards may be used in groups to specify several networks on a
structure. All network cards for a network configuration must occur
together with no other cards (except TL cards) separating them. When
the first NT card is read following a card other than an NT or TL
card, all previous network and transmission line data are destroyed.
Hence, if a set of network data is to be modified, all network data
must be input again in the modified form. Dimensions in the program
limit the number of networks that may be specified. In the present
NEC deck, the number of two-port networks (including transmission
lines) is limited to thirty, and the number of different segments
having network ports connected to them is limited to thirty.
<p>
<li>One or more network ports can be connected to any given segment.
Multiple network ports connected to one segment are connected in
parallel.
<p>
<li>If a network is connected to a segment which has been impedance
loaded (i.e., through the use of the LD card), the load acts in
series with the network port.
<p>
<li>A voltage source specified on the same segment as a network port is
connected in parallel with the network port.
<p>
<li>
Segments can be impedance-loaded by using network cards. Consider
a network connected from the segment to be loaded to some other
arbitrary segment as shown in figure 17. The admittance matrix
elements are Y<sub>11</sub> = 1/Z<sub>l</sub>, Y<sub>12</sub> = 0,
and Y<sub>22</sub> = infinity (computationally,
a very large number such as 10<sup>10</sup>). The advantage of using this
technique for loading Ls that the load can be changed without causing
a recalculation of the structure matrix as in required when LD
cards are used. Furthermore, in some cases a higher degree of
structure matrix symmetry can be preserved because the matrix
elements are not directly modified by networks as they are when
using the LD cards. (Consider for instance a loop with one load
where the loop is rotationally symmetric until the load is placed on
it.) The disadvantage of the NT card form of loading is that the
user must calculate the load admittance, and this value does not
automatically scale with frequency. Obviously, in the above
schematic, replacing the short with an impedance would load two
segments. At a segment at which a voltage source is specified, the
effect of loading by the LD nd NT cards differs, however, since the
network is in parallel with the voltage source while the load
specified by an LD card is in series with the source.
<p>
<li>Use of network cards (NT) after any form of execute requires the
recalculation of the current only.
<p>
<li>NT and TL cards do not affect structure symmetry.
<hr>
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