The design of simulated antenna is shown in Fig. 3.1. As can be seen from the figure, the Yagi-Uda antenna was built on a FR4 substrate (εr = 4.4) with the thickness of 1.6 mm. The design consists of one director element, a driven element and a ground plane acting as a reflector. To enhance the gain of the antenna coupling microstrips and metal plate were placed, that focus the entire beam towards a driven dipole.
Fig. 4.1: Simulated Yagi-Uda antenna
4.3 SIMULATED RESULTS
After simulating the design different parameters of antenna are obtained such as return loss, gain, directivity, VSWR and radiation efficiency.
(a) Return loss:
Return loss is related to both standing wave ratio (SWR) and reflection coefficient (Γ). Increasing return loss corresponds to lower SWR. Return loss is a measure of how well devices or lines…show more content… 4.4: Simulated Directivity of Yagi-Uda antenna
(d) VSWR:
For a radio (transmitter or receiver) to deliver power to an antenna, the impedance of transmission line well matched to the input impedance of the antenna. VSWR is a measure that numerically describes how well the impedance of antenna is matched to the transmission line. VSWR (voltage standing wave ratio) is also referred to as standing wave ratio. It is a function of the reflection coefficient, which describes the power reflected from the antenna.
VSWR is defined by the following formula, which is given in eqn 3.2.
VSWR= (1+ Γ)/(1- Γ) (3.2) Where, Γ is the reflection coefficient
The VSWR is always a real and positive number for antennas. The smaller the VSWR is, the better the antenna is matched to the transmission line and the more power is delivered to the antenna. The minimum VSWR is 1.0. In this case no power is reflected from the antenna, which is ideal. Fig. 3.5 shows VSWR of 1.4 at 5.2 GHz, which is less than