Design Of Microstrip Antenna And LNA For WLAN Application

With the rapid development of wireless communication technology, there is an ever-increasing application scope of WLAN. As an important part of WLAN, the antennas have the most direct impacts on the performances of WLAN. Microstrip antenna is a good choice for WLAN, because it has some principal advantages, such as small size, light weight, low profile and so on. So it is necessary to design novel microstrip antenna for the standards of WLAN. In this paper, three microstrip antennas and a low noise amplifier for Dalian Tian-sheng Science Equipment.Ltd are designed.Firstly, the design and measurements of a dual-fed type circularly polarized patch antenna are presented in this paper. For the proposed antenna, an L-probe and an aperture are utilized to feed the patch orthogonally. A3dB-bridge combiner is connected to the feeds to generate circular polarization. A low-permittivity foam material is utilized to increase impedance bandwidth. The experimental results show that the antenna has the merits of low return loss, wide3-dB axial ratio bandwidth, and high gain. Secondly, a microstip-fed circularly polarized monopole antenna is proposed in this paper. This antenna has the merits of small volume, low cost, and wide impedance bandwidth.For the proposed antenna, an asymmetric structure is used to provide an orthogonal component distinct from its original linear polarization. The deforming ground plane and patch are utilized to generate circular polarization. The two antennas both satisfy the application of WLAN IEEE802.11b standard. Lastly, a new dual-band microstirp patch antenna is studied in this paper. For the proposed antenna, an aperture coupled feed structure is proposed for good impedance matching. Dual-band characteristic is produced by using slot E. The experimental results show that the resonant frequencies of the antenna are2.45GHz and5.25GHz, relative bandwidth are8.2%and12.4%. It satisfies the protocol IEEE802.11g of WLAN.Low Noise Amplifier (LNA) is an important component of the RF receiver front-end circuit. In order to let the system demodulate the needed information and data better, it is always used to amplify the weak signal received antenna from the air and to reduce noise interference. By using the EDA software ADS2009of Agilent, a LNA is designed and simulated with the key features of low noise coefficient and high power gain. The LNA completely covers2.4GHz～2.4835GHz band and satisfies the protocol IEEE802.11b of WLAN.