A microstrip antenna generally consists of a dielectric substrate sandwiched between
a radiating patch on the top and a ground plane on the other side. Microstrip
antennae have advantages such as low profile, conformal, light weight and low
manufacturing cost (Raju, 2006).
Many methods were developed to increase the bandwidth of antennae such as
increase of substrate thickness and use of low dielectric substrate (Kumar and Ray,
2003; and Balanis, 2005). The principal disadvantages of microstrip antenna are narrow
bandwidth, poor efficiency and size (Waterhouse et al., 1998). The miniaturization
of antenna and improvement in bandwidth can be achieved by etching the slot in
ground and patch of microstrip antenna of proper length and width (Dey and Mittra,
1996; and Vani et al., 2006). It was demonstrated that as the slot length and width
increased, the resonant frequency shifted towards lower side (Raj Kumar et al., 2009).
The change in the resonance frequency is minimum for the longest slot length,
whereas it is maximum for the minimum slot length. A compact triple band antenna
using a combination of both T-shaped and S-shaped forming comblike structure is
discussed (Brajlata and Prachi, 2014). A comparative analysis has been made for the
U and half U, and and half designs are proposed by reducing area to 50% and
increasing the substrate thickness (air gap) (Brajlata et al., 2014).
|
