V and Rhombic Antenna

Presented by: Ashish Kumar Singh Roll no.

09MUBECE012 ECE Third year

IntroductionTwo long wire antennas (called legs) are

arranged in the form of horizontal V,fed at the apex as shown in fig.

Salient Features of V-antennaThe excitation to each wire is out of phase.It offers greater gain and directivity when

length of each leg or wire is increased.The apex angle ranges between 36° to 72° for

V antennas of 8λ to 2λ length.It is easy to construct and they are cheap. It is two types- 1-Resonant 2- Non-Resonant

Radiation pattern1-Resonant V antenna-

Radiation pattern (contd.)2-Non Resonant V antenna

The optimum included angle , α is α=-149.3( l/ λ)3+603.4 ( l/ λ)2- 809.5 ( l/ λ )

+443.6The maximum directivity is D=2.94 ( l/ λ )+1.15 ,for 0.5< ( l/ λ )<3

Rhombic Antenna

Rhombic AntennaStructure and construction

4 wires are connected in rhombic shape and terminated by a resistor.

Mounted horizontally and placed > λ/2 above ground

Directional property The fields in the X right direction is additive Fields in other directions are self cancelled

out.

Rhombic AntennaStructure and construction

4 wires are connected in rhombic shape and terminated by a resistor.

Mounted horizontally and placed > λ/2 above ground

Directional property The fields in the X right direction is additive Fields in other directions are self cancelled

out.

Radiation pattern

3-D Radiation pattern

Features of Rhombic AntennaAdvantages

Easier to construct Its input impedance & radiation pattern are

relatively constant over range of frequencies. Maximum efficiencyHigh gain can be achieved

Disadvantages large site area & relatively large side lobes

Design Parameters of Rhombic antennas-Rhombic height,H H= λ/4sin Φ• The Tilt angle, θ θ= 90°-elevation angle = 90° -Φ• The leg length, L L= λ/2sin2 Φ = λ/2cos2 θ

ApplicationsThe rhombic antenna is widely used for long-

distance, high-frequency transmission and reception.

In point-to-point communications. Radio communications.Short wave radio broadcasting.For long distance communications.