Abstract:
Like any other field, effective communication is critical in warfare. The earliest military
communications were delivered by runners. Later, communications progressed to visual
and audible signals, and then advanced into the electronic age. Present day military
forces conduct intense and complicated communicating activities on a daily basis, using
modern telecommunications and computing methods. One of the radio sets that is used
by Pakistan Army for this purpose is the Software Designed Radio (SDR) set. Most of
the communication in armed forces is carried out in VHF and UHF bands. SDR based
radio sets used in Pakistan Army has limited performance due to lack of antenna that is
optimized for all frequencies in range of 30 to 512 MHz. There are separate antennas
optimized for different sub-bands in 30 – 512 MHz band which are needed for specific
sub band. There is a need for an all range (30 to 512 MHz) Omni-directional whip
antenna that can be integrated with man pack so that the user does not need different
antennas every time frequency is changed to different sub bands. Therefore, a
broadband monopole antenna with a very low-cost mechanical structure is proposed.
This monopole with inductor/resistor (LR) loading circuits is designed to operate in the
frequency range of 30-512 MHz. By choosing optimized locations of LR loads, the
radiation pattern is controlled. Meanwhile, the VSWR is adjusted by an input matching
circuit, tuning a number of LR loads, and using a transmission line transformer. The
impedance matching is improved in whole frequency bandwidth and antenna gain is
also increased than in the existing antennas. The antenna is considered to be used in
portable applications.
