Modern nec2++ grammar for antenna geometry.

This is a parser for NEC antenna geometry files written for the ANTLR parser generator. At the moment it is rudimentary.

The goal is to update the NEC parser to handle a more modern grammar, and to allow useful things like multi-line comments e.t.c.

In addition, this will replace the terrible parser code that currently exists, and will hopefully catch errors like wires accidentally intersecting as at parse time.

Requires ANTLR

aptitude install libantlr-dev libantlr-java

Also requires lapack libraries.

aptitude install math-atlas-dev

Testing

Just build in the current directory

make 
make test_clean
make test_all

New parser for NEC cards

The grammar is in the file nec.g. This is an ANTLR grammar for the existing NEC2 card deck for describing antennas.

New Language

The new language for nec++ will be more explicit and easy to read. It will also allow comments anywhere inside the code. In addition it will not depend on whitespace to skip over missing parameters, and therefore will be far more robust.

/* This is a comment */
geometry {
  w0 = wire(start=[1,2,3], end=[2,3,4], r=0.01, n=5);
  w1 = wire(start=w0.end,  end=[2,3,5], r=0.01, n=5);
  arc(origin=[0,1,2], arc_radius=1.0, r=0.01 );
  helix();
  patch();
  scale(3.0);
}

ground {
  type=PERFECT;
}

excitation {
  type=VOLTAGE;
  segment=w0.0; /* Segment indexing starts at 0 */
  freq=range(start=1.575GHz, end=1.675GHz, n=5);
  extended_thin_wire_kernel = false; /* default */
}
    
radiation_pattern {
  mode = "normal";
  theta = range(start=0.0, end=180, n=30);
  phi = range(start=0.0, end=90, n=30);
}

execute();

Expression Syntax:

{ id = } TYPE([param=expression]*) ;