Broadband Planar Antennas: Design and Applications

2

Broadband Microstrip Patch Antennas

2.1 INTRODUCTION

Microstrip antennas and arrays have attracted much attention from researchers and engineers and have been used extensively in RF and microwave systems, such as communications, radar, navigation, remote sensing, and biomedical systems. Microstrip antennas can take a variety of forms, such as patch, dipole, slot, or a traveling-wave structure, designed for specific applications. Examples are illustrated in Figures 2.1–2.3.

Patch or patch-like radiators feature unique characteristics and have been studied in depth. They offer several important advantages:

• Low profile. The thickness of a microstrip patch antenna is usually less than 0.03 λ_o (λ_o is the operating wavelength in free space).
• Light weight. A microstrip patch antenna is usually made from perfectly electrically conducting (PEC) foil affixed on a dielectric substrate.
• Conformability to surfaces of substrates. A microstrip patch antenna may be of a planar or nonplanar surface, which can completely conform to the surface of the dielectric substrate it is attached to.
• Low cost. A microstrip patch antenna is commonly fabricated using an inexpensive printed-circuit technique. The substrate is usually the most costly portion of the antenna.
• Integration with other circuits. It is easy to completely integrate a microstrip patch antenna on a printed-circuit board (PCB) with other planar circuits.
• Versatility. A microstrip patch antenna is very versatile in terms of impedance, ...