A new wideband modified biquad antenna at VHF for communication systems

A new wideband antenna operating at VHF band for communication systems is designed and implemented in this paper. The antenna at first consists of two quad antenna (Biquad). Gain of around 5 dB of this section are demonstrated; narrower beam widths and a further increase of gain is achieved using a reflector. For further increase of gain and beam width in azimuth plane, some passive elements are added. Simulated results show that 10-dB impedance bandwidth ranges from 125 to 210 MHz (bandwidth of more than 40%), with the voltage standing wave ratio (VSWR) less than 1.5 and a good radiation pattern with 11.5-dBi gain is earned. To validate the design, a prototype of antenna is fabricated and tested. Measured results of a full-scale prototype fabricated with aluminum wipe are in good agreement with simulated ones, which demonstrates the antenna's potential applications in lots of application in VHF Band.