Wednesday, September 14, 2016

All antennas are not created equal

In today’s scenario, people expect more convenient ways to access the network. In this case, Wireless (WLAN) offers tangible benefits over traditional wired networking. Antenna a key element used to get better coverage. This article highlights the replacement of traditional Omni directional antenna with proposed Double Bi-quad antenna which is cost effective high gain, directivity and easy to fabricate. Current high gain antennas on the market that meet these specifications are expensive and cannot cover a larger distance. The proposed antenna consists of four equally sized squares radiating element on a printed circuit board with 50 ohm SMA connector which produces high directivity and peak gain of 12.9 dBi and works at 5.8 GHz.
As mentioned above, Wireless (WLAN) offers tangible benefits over traditional wired networking. Wi-Fi (Wireless Fidelity) is a generic term that refers to the IEEE communication standards for Wireless Local Area Networks (WLANs). The wireless network is formed by connecting all the wireless clients to the Access Point (AP). Single access point can support up to 30 users and can function within a range of 100 – 150 and 300 feet indoors and outdoors respectively. The AP has the traditional Omni directional antenna. The coverage area depends on the location of the access point is actually placed. Omni directional antenna can operate over narrow bandwidth and requires tuning and phasing. Omnidirectional antennas radiate roughly the same pattern all around the antenna in a complete 360° pattern. Directional or directive antennas have a  beam width that is much narrower than sectorial antennas and they have the highest gain and are therefore used for long distance links. Point to be noted is that when an antenna transmits the signal in a certain direction stronger than in the other directions, it also receives the signal in that direction better than in the other directions due to its reciprocal property. A directional antenna is designed not solely for range extension but can also be utilized for interference reduction (signal quality improvement) due to the fact that a directional antenna transmits and receives in a certain direction better than in the other directions thus both transmission and reception of signals in the unwanted directions are minimized. Moreover, a directional antenna can be deployed to limit the coverage area of the AP to a desired area. This is beneficial when uusers, who want to connect to the network, are concentrated in a certain area. There are many companies selling highly-directional (high-directivity) antennas in the market. However, many of those commercial antennas can be constructed in a workshop at home. This leads to the main objective of this paper, which is to design a double biquad 5.8GHz antenna.
Parameters of antenna include radiation pattern, beam width, power, directivity, gain, aperture, radiation resistance. In the field of antenna design the term radiation pattern (or antenna pattern or far-field pattern) refers to the directional (angular) dependence of the strength of the radio waves from the antenna or other source. The beam width of an antenna is a very important figure of merit and often is used as a trade-off between it and the side lobe level; i.e, as the beamwidth decreases, the side lobe increases and vice versa.

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