Antenna Design

Lab 07 - Friis Transmission Equation

I. Simulation

Dipole dimensions:

Feeding: Center-fed with a discrete port with source impeance of 50 W

Design frequency: f ₀ = (1000 + PIN/1000) MHz

실습조교 PIN = 0000

Dipole end-to-end length: L = 0.40 λ

Dipole diameter: d = L/15

Dipole feed gap at the dipole center: g = d/2

Dipole material: PEC

Frequency range: 0.5f₀ to 1.5f₀

Use Dipole #1 and Dipole #2 with dimensions as above.

Dipole #1 arm: Direction = z, dipole center at y = 0 and x = 0

Dipole #2 arm: Direction = z, dipole center at y = R and x = 0

For R = 0.25 λ

1-1. Plot the antenna structure.

1-2. Plot Plot |S11|, |S21| in dB.

1-3. Find |S21| (dB) at f₀.

1-4. Plot (in polar form) the co-polarizaed gain Gtheta at f₀ of a dipole in the directioin of the other dipole on the q = 90° plane. Find the Gtheta (dB) in the direciton of the other dipole. The presence of the other dipole may change the omnidirectional pattern of an isolated dipole.

1-5. Find |S21| (dB) at f₀ using Friis transmission equation . Note that |S21|² = Ptx / Prx

For R = 0.5 λ, repeat the above.

2-1.

2-2.

2-3.

2-4.

2-5.

For R = 1.0 λ, repeat the above.

3-1.

3-2.

3-3.

3-4.

3-5.

II. Discussions

1. Compare |S21| (dB) by CST Studio with |S21| (dB) by Friis equation.

	R = 0.25 λ	R = 0.5 λ	R = 1.0 λ
1. |S21| (dB), CST Studio
2. Antenna gain Gtheta (dB) in the other dipole direction
3. Path loss: (λ/4πR)^2 (dB)
4. |S21| (dB), Friis equation
5. |S21| difference (dB) (1-4)

2. Find the minimum distance where the Friis equation is accurate within ±1 dB. Note the Friis equation is accurate when both antennas lie in the far-field region of the other antenna.