Broadband impedance matching for tactical VHF/UHF antennas

Abstract

In designing any type of broadband antenna, either of single or multiple elements much of time and recourses are consumed for proper impedance matching. Impedance matching is broadly classified into two types i) Distributed matching ii) Lumped element matching. Firstly Distributed matching, which leads to modification of antenna geometry itself & secondly by lumped element, which requires to use lump element i.e. capacitor resistor or inductors to do impedance matching between load and source This thesis introduces a hybrid technique of impedance matching with the combination of distributed and lumped component for tactical VHF/UHF monopole/dipole antenna .The major objective of this thesis is to reduces the antenna losses in operational bandwidth such that antenna gain positive in most of bandwidth and VSWR to be lower than 3. Further antenna design is feasible for portability and capable of handling high power up to 100 watts CW. Three antenna models for VHF, UHF, and VHF-UHF band are proposed for high power and broad impedance bandwidth applications. For a first prototype antenna, a bandwidth of 10:1 was achieved in VHF band antenna. The operational bandwidth of this band antenna is 250 MHz to 1GHz. For a second prototype antenna, a bandwidth of 200 MHz to 520 MHz was achieved in UHF band antenna with positive gain pattern throughout the bandwidth. For a third prototype antenna, a bandwidth of 21:1 was achieved in VHFUHF band antenna. The operational bandwidth of this band antenna is 84MHz to 890 MHz, with the positive gain pattern in most of the frequency band. The microstrip patch antenna for UWB application from 3.1 GHz to 10.6 GHz is also proposed and simulated Measured results of all the designed prototype antennas are reported. The result found to be similar with simulated results Simulation and measured result confirm our premise.