text: Exp-13-AWP | Lab Manual | Electronics tutorial | Electronics Tutorial
  Dolph-Tchebyshev array
  Title: Dolph-Tchebyshev array
  · To sketch the radiation pattern Dolph-Tchebyshev array.
  · To compute performance parameters.
  Objectives: Model Dolph-Tchebyshev array to analyze the performance parameters
  Apparatus: PC, EM Simulation software
  coefficients are related to Tschebyscheff polynomials. A Dolph-Tschebyscheff array with no side lobes (or side lobes of −∞ dB) reduces to the binomial design.
  1. Click anywhere on the information window title bar and enter name of antenna you want to design and simulate then click Ok or press the <Enter> key
  2. Click anywhere on the selection button to its left. Enter desire frequency in the dialog text box, and click Ok or press <Enter>. It will automatically calculate wavelength and get displayed into wavelength menu.
  3. Open the Wires Window by clicking on the Control Center "Wires" line, or the selection button to its left. Position the Wires and View Antenna Windows for convenient viewing. The position of each wire in space is specified by giving its x, y, and z coordinates. These coordinates represent distances from the origin.
  e.g. for dipole that lies along X-axis at origin of length 0.5m has its X=0.25,Y=0,Z=0 (for end-1); X=-0.25,Y=0,Z=0 (for end-2). The last column is to define the number of segments for the wire. Total 20 segments are allowed for EZNEC-Demo version. As number of segments increases, accuracy of current distribution and thereby radiation pattern increases.
  4. In the Sources Window grid, you can see that there's one source (source no. 1), which is placed on wire #1, 50% from end 1. This is where we want the source to be. However, this is a good time to practice a little with the Sources Window. The source type, shown in the Type column, is a current source. The Sources Window also shows the source amplitude and phase, in this case one ampere at zero degrees. When a model contains only a single source, the magnitude, phase, or type have no effect on the pattern or source impedance.
  5. Click on the Ground Type line, and select real. The height of the antenna will determine which ground model we use. If you have a fast computer, you can always choose High Accuracy analysis unless you need to make a connection to ground. When we changed the ground type to Real, one ground medium was created. The conductivity and dielectric constant of newly-created grounds can be set for your local ground conditions by means of the Control Center Options menu Default Ground Const selection. The values initially used by EZNEC are those of "average" or "good" ground (conductivity of 0.005 S/m, dielectric constant of 13).
  6. Click on the Units line or the selection button to its left, then select meter, and Ok.
  7. Click on the Plot Type row in the Control Center and select either of elevation, azimuth or 3D-pattern.
  8. Save the antenna description by clicking the Save As action button.
  9. Click the action button. FF Plot; it will show you the radiation pattern and beam width, gain etc. Under view option of 3D plot it is also possible to see 2D pattern of radiation.
  Dimensions of array element (half wave dipole )
  1. Calculate wavelength=>
  2. Length of antenna=> meter.
  3. Spacing between element=>
  For Pascal's triangle
  Calculate coefficient of binomial array (as amplitude of excitation) using following formula
  Where, n= number of elements.
  An array consisting a no. of equidistant dipoles of equal size, fed with the same currents and phase is called:(a) end fire array (b) back fire array (c) broad side array (d) binomial array
  Choose the correct statement:(a) Both Binomial and uniform amplitude distributions are special cases of Dolph-Tchebyscheff distribution.(b) Both edge and uniform amplitude distributions are special cases of Dolph-Tchebyscheff distribution.(c) Both Binomial and edge istributions are special cases of the Dolph-Tchebyscheff (D-T) distribution.(d) All the three distributions listed in (a, b & c) above are special cases of Dolph-Tchebyscheff distribution