As the dielectric constant of the substrate increases, the antenna bandwidth decreases which increases the Q factor of the antenna and therefore decreases the impedance bandwidth. The dielectric loading of a microstrip antenna affects both its radiation pattern and impedance bandwidth.
![surface waves patch antenna array surface waves patch antenna array](https://d3i71xaburhd42.cloudfront.net/5ba36f114c4a2ae4d5ff5cf54b4134d232d87e81/23-Figure1.12-1.png)
An early model of the microstrip antenna is a section of microstrip transmission line with equivalent loads on either end to represent the radiation loss. The resonant length of the antenna is slightly shorter because of the extended electric "fringing fields" which increase the electrical length of the antenna slightly. As the antenna is loaded with a dielectric as its substrate, the length of the antenna decreases as the relative dielectric constant of the substrate increases. When air is used as the dielectric substrate, the length of the rectangular microstrip antenna is approximately one-half of a free-space wavelength. It is approximately of one-half wavelength long. The most commonly employed microstrip antenna is a rectangular patch which looks like a truncated microstrip transmission line. This unique property allows patch antennas to be used in many types of communications links that may have varied requirements.
![surface waves patch antenna array surface waves patch antenna array](https://ars.els-cdn.com/content/image/3-s2.0-B9780121709600500438-f41-17-9780121709600.gif)
Patch antennas can easily be designed to have vertical, horizontal, right hand circular (RHCP) or left hand circular (LHCP) polarizations, using multiple feed points, or a single feedpoint with asymmetric patch structures. Īn advantage inherent to patch antennas is the ability to have polarization diversity. Such an array of patch antennas is an easy way to make a phased array of antennas with dynamic beamforming ability. The ability to create high gain arrays in a low-profile antenna is one reason that patch arrays are common on airplanes and in other military applications. Patch arrays can provide much higher gains than a single patch at little additional cost matching and phase adjustment can be performed with printed microstrip feed structures, again in the same operations that form the radiating patches. It is relatively easy to print an array of patches on a single (large) substrate using lithographic techniques. A single patch antenna provides a maximum directive gain of around 6–9 dBi. They are usually employed at UHF and higher frequencies because the size of the antenna is directly tied to the wavelength at the resonant frequency. Microstrip antennas are relatively inexpensive to manufacture and design because of the simple 2-dimensional physical geometry.
Surface waves patch antenna array skin#
Because such antennas have a very low profile, are mechanically rugged and can be shaped to conform to the curving skin of a vehicle, they are often mounted on the exterior of aircraft and spacecraft, or are incorporated into mobile radio communications devices. Some patch antennas do not use a dielectric substrate and instead are made of a metal patch mounted above a ground plane using dielectric spacers the resulting structure is less rugged but has a wider bandwidth. Common microstrip antenna shapes are square, rectangular, circular and elliptical, but any continuous shape is possible. A patch antenna is a narrowband, wide- beam antenna fabricated by etching the antenna element pattern in metal trace bonded to an insulating dielectric substrate, such as a printed circuit board, with a continuous metal layer bonded to the opposite side of the substrate which forms a ground plane. Antennas using patches as constitutive elements in an array are also possible. The most common type of microstrip antenna is commonly known as patch antenna.
![surface waves patch antenna array surface waves patch antenna array](https://d3i71xaburhd42.cloudfront.net/5ba36f114c4a2ae4d5ff5cf54b4134d232d87e81/10-Figure1.1-1.png)
Microstrip antennas have become very popular in recent decades due to their thin planar profile which can be incorporated into the surfaces of consumer products, aircraft and missiles their ease of fabrication using printed circuit techniques the ease of integrating the antenna on the same board with the rest of the circuit, and the possibility of adding active devices such as microwave integrated circuits to the antenna itself to make active antennas The radio frequency current is applied (or in receiving antennas the received signal is produced) between the antenna and ground plane. The antenna is usually connected to the transmitter or receiver through foil microstrip transmission lines. Most microstrip antennas consist of multiple patches in a two-dimensional array.
![surface waves patch antenna array surface waves patch antenna array](https://ai2-s2-public.s3.amazonaws.com/figures/2017-08-08/047263f4a6e50c48a55308836704423e4e6e4891/4-Figure8-1.png)
An individual microstrip antenna consists of a patch of metal foil of various shapes (a patch antenna) on the surface of a PCB ( printed circuit board), with a metal foil ground plane on the other side of the board. They are mostly used at microwave frequencies. In telecommunication, a microstrip antenna (also known as a printed antenna) usually means an antenna fabricated using photolithographic techniques on a printed circuit board (PCB). Diagram of the feed structure of a microstrip antenna array.