A Brief Overview of the Zeland Software Suite
For example:
1. We can quickly surpass the frequency for which NEC is adequate to our task. It is desirable to maintain a segment length-to-wire diameter ratio of 1:1 minimum and higher, if possible. We also need to maintain about 10 segments per wavelength and more if possible. A 1 GHz, a wavelength is 0.3 m (300 mm) long. The segments for a minimally segmented element would be 0.03m (30 mm) long, barely enough for a fat 1″ (25.4 mm) element–assuming that we have no odd geometries that require more segments per wavelength. Alternatively, a helix depends upon many short, straight wires for simulation, and hence the need for segments much shorter than 0.1 wavelength. The allowable wire diameter shrinks accordingly. Figure 1 shows a pair of shapes that–at upper UHF and high frequencies–often surpass NEC limitations. And these are but two of many.

2. NEC and MININEC calculations rest upon a thin wire foundation, a thin ROUND wire. Above about 400 MHz, it begins to make sense to fabricate antennas on circuit boards, using elements that are flat strips rather than round wires. Up to a point, we can model such antennas within NEC or MININEC using equivalent round wires. However, the more complex the structure, the less adequate the substitutes are. Parasitic relationships begin to depend upon how much surface area is facing the next element. NEC and MININEC cannot easily adjust this dimension and still sustain the overall cross-section area of the conductor.
3. As we move still higher into the UHF region, it becomes practical to integrate into an antenna design any required transmission lines to terminals, impedance transformation networks, phasing lines, and even a variety of filters. All can be fabricated using a single substrate or a coherent collection of substrates. Many facets of the design may make use of the substrate properties to create lumped components or their equivalents. We may further integrate these design elements with 3-dimensional shapes, such as horns. But each element on the original substrate also has 3-dimensions. The wire-grid potentials of NEC often fall short of being able to deal with this degree of integration.
These are only some of the reasons designers working in the wireless realm have turned in part to a different order of software to simulate their complex structures that include antennas. Some of the desirable features of such software would include the following:
I leave this list without an end, because an engineer’s wish list and a programmer’s challenge are equally unending.
Software packages aimed at meeting these needs do exist. They are large, complex, and often require special training–not to mention lots of trial and error experience–to use effectively. One such program that I recently had the chance to review is Zeland Software’s suite. The suite is usually called IE3D, but actually consists of a collection of modules, each with specific specialties, but many overlapping functions:
IE3D is historically the first of the stand-alone modules offered by Zeland (1993). Now in release 8, it is also the best documented of the modules, with well over an inch-thick manual devoted to it. The name “IE3D” captures two of the main features of the modules. “IE” is short for an integral equation, method of moment, full-wave electromagnetic simulator. Unlike NEC programs that require very large models using wire-grid techniques, the “3D” portion of the IE3D title indicates that the program uses a 3-dimensional non-uniform triangular and rectangular mixed meshing scheme to capture complex shapes. The difference between a wire grid shape and the IE3D technique appears in Figure 2.

The program is geared toward microwave and millimeter-wave applications with more than antennas (both normal and patch) in mind. It is also aimed at uses in integrated circuit and filter design, EM scattering analysis, and other applications involving coaxial and digital circuits. The module solves for current distribution, network parameters, near fields, and radiation patterns. The program has the ability to model arbitrary shapes in multiple layers within a complex dielectric environment. Figure 3 shows a sample of a 3-dimensional shape set that includes metal thickness as well as area, terminals, and connection jumpers.

IE3D is subdivided into several sub-programs. MGRID is the starting point, since it comprises the layout editor for constructing a geometry for analysis. Every shape to be simulated is composed of a set of polygons, and each polygon is described by a set of vertices (or corners). Vertex matching is a condition of ensuring the electrical connection between two adjacent polygons.
Much of the IE3D manual is devoted to mastering the art of object or circuit construction. Because of its power, MGRID requires a considerable learning curve for full mastery. Indeed, Zeland offers seminars for mastering basic techniques, and it is likely that these seminars are the best and quickest introduction to the art of geometry fabrication within the program. The review period for the program was not sufficiently long for me to fully acquire a decent mastery of the techniques. Hence, all illustrative graphics are downloads from Zeland. However, I was able to replicate a number of useful shapes to get a feel for what is possible. And what is possible is considerable for work in the 1-25 GHz range and beyond.
For nodal circuit simulation and parameter display, the program contains a module called MODUA. There is a post-processor called CURVIEW for the display and animation of current and field distribution. Equally important to antenna and EMC interests are PATTERNVIEW and FIELD, post processor modules for examining radiation patterns and calculating near fields, respectively. Radiation patterns are routinely displayed in 3-dimensional terms, with color indications for field strength, as illustrated in Figure 4. However, the vivid color graphics is backed up by an impressive array of rectangular and polar plots. Equally impressive are the number of ways in which the user can compare output data from models. The latest “powerpack” release of IE3D also contains a genetic optimizer capable of handling a considerable number of variables and optimizing goals.

The user in effect must custom design his purchase or licensing for this program according to a careful analysis of present and future needs. The pricing differential between the “limited” package and the “powerpack” version of IE3D is better than 2:1. The limited package restricts the user to 1,000 unknowns of less. The intermediate package removes this limitation, but does not include 3 features available only in the powerpack edition: the genetic optimizer, magnetic current modeling for slot structures, and the higher efficiency iterative matrix solver.
Although billed a complementary to IE3D, Zeland almost makes the case for replacing IE3D with Fidelity, the finite-difference time-domain (FDTD) program. Introduced in late 1997, Fidelity contains within its overall collection modules that are comparable to those in the IE3D package: a “Workshop” for the geometry construction phase of the work, Fidelity proper as the FDTD simulation core, MODUA as a schematic editor and parameter display unit, a current animator, and the same pattern-view module as used in IE3D.
Nonetheless, FDTD techniques, as used in the Fidelity package, can produce impressive results with objects consisting of highly complex combinations of conductive and dielectric materials. Figure 5 shows the E-field and the H-field that result from a plastic covered object–in this case, a typical hand-held transceiver.

Perhaps one of the most complex objects–and yet one of the most important in an age of cell phones–is the human head. As Figure 6 shows, Fidelity contains a rotatable model of the human head that can form the basis for any number of more complex assemblages. The figure adds a transceiver with a projecting antenna as a case in point. Just how finely one might detail the interior layers of the head to correspond with the variable density and material that actually compose the human head is not completely clear at first sight. However, it is a foundation upon which to build truly significant models of the interaction of RF energy with the most critical part of human anatomy.

Not included in the manual are two interesting modules offered by Zeland. One is of their own making: COCAFIL: a suite to design and analyze waveguide-coupled cavity filters so widely used in all upper UHF/SHF applications. Figure 7 shows a sample screen for the design of a specific filter.

Still further into the Zeland offerings is a transmission line analysis and synthesis module called LineGauge. The basic program is a free download from the Zeland site (http://www.zeland.com). A “professional” version is also available, but is not free. Figure 8 shows a sample LineGauge screen for a coaxial cable. However, the program–as indicated by the entries at the right of the figure–covers a wide range of transmission line types.

Originally posted on the AntennaX Online Magazine by L. B. Cebik, W4RNL
Last Updated : 29th January 2025