Creating the Model

Create the model in CADFEKO. Define any ports and sources required for the model. Specify the operating frequency or frequency range for the model.

1. Define the following variables:
   • freq = 46.29e6 (The operating frequency.)
   • lambda = c0/freq (The wavelength in free space.)
   • tau = 0.93 (The growth factor.)
   • sigma0 = 0.7 (Spacing)
   • sigmaN = sigma(N-1)/tau, where N is iterated from 1 to 11 with an increment of 1.
   • d0 = 0 (Position of the first element.)
   • dN = d(N-1) – sigmaN, where N is iterated from 1 to 11 with an increment of 1.
   • len0 = 2 (Length of the first element.)
   • lenN = len(N-1)/tau, where N is iterated from 1 to 11 with an increment of 1.
   • rad0 = 0.00667 (Radius of the first element.)
   • radN = rad(N-1)/tau, where N is iterated from 1 to 11 with an increment of 1.
   • Zline = 50 (Transmission line impedance.)
   • Zload = 50 (Shunt load resistance.)
2. Create twelve dipoles.
   1. Create lines 0 to N, where N is iterated from 0 to 11 with an increment of 1.
      • Start point: (dN, -lenN/2, 0)
      • End point: (dN, lenN/2, 0)
   2. Add a wire port to the middle of the line.
   3. Number the ports from 0 to 11.
3. Add a voltage source to the first dipole¹ (1 V, 0°, 50 Ω).
4. Create eleven transmission lines to connect the dipoles.
   1. Create transmission lines 1 to N, where N is iterated from 1 to 11 with an increment of 1.
      • Definition method: Z0, length, attenuation
      • Transmission line length: sigmaN
      • Real part of Z0 (Ohm): Zline
      • Imaginary part of Z0 (Ohm): 0
      • Attenuation (dB/m): 0
      • Select the Cross input and output ports check box to allow the correct transmission line orientation.
5. Connect TransmissionLineN between Port(N-1) and Port(N) in the Network schematic view, where N is iterated from 1 to 11 with an increment of 1.

   
   

   

   
   Figure 1. The network schematic view showing the connected transmission lines, general networks and ports.

6. Define a shunt load using a general network.
   • Specify the one-port Y-matrix manually.
   • Y₁₁ = 1/Zload
7. View transmission line 11 in the Network schematic view.
   1. Connect the general network to port 11.
8. Set the continuous frequency range from 35 MHz to 60 MHz.