The Design And Study Of UWB Antennas

Four UWB antennas are presented and investigated in this paper: double printed dipole antenna, U-shape arm double printed dipole antenna, band-notched double printed dipole antenna and band-notched circular ring monopole antenna.Ultra wideband (UWB) technology has become one of the promising candidates for short range wideband communications. Antenna is one crucial part of UWB systems. The performance of the antenna directly affects the quality of the communication. The design of UWB antenna is obviously different from that of traditional narrow band antenna. All the parameters must be considered over the UWB band from 3.1 GHz to 10.6GHz .Not only the standing wave ratio, gain, radiation patterns, but also the transfer function, impulse response in time domain should be considered. Besides, the UWB antenna must be easy to integrate with other parts of the system.All antennas presented in this paper are planar printed structure and fed by microstrip lines. In order to avoid potential interference with 5GHz WLAN, UWB antenna with band-notched characteristics are presented by inserting slots on the radiators. Simulations using the EM simulator software CST and experiments are combined in the paper to design and investigate the antennas. Frequency parameters were measured by vector network analyzer. Equivalent network model was built to obtain the transfer function of the system and UWB antenna. Inverse Fourier transform was used to get the impulse response in time domain.Both the simulation and experimental results show that all the antennas presented are able to work in 3.1～10.6GHz UWB band. The radiation patterns are stable to frequency; Magnitudes of system transfer functions are flat and the phases are linear. For band-notched double printed dipole and band-notched circular ring monopole antenna, band-notched characteristics are achieved over 5～6GHz.The UWB antennas with small size presented in this paper, which are easy for integrations, are suitable for UWB applications and possess very strong practicality. The equivalent network model method and transfer function concepts have great reference values for other study of UWB antenna. The design and study works done in this paper are helpful to promote the development and improvement of the UWB antenna theory and technology.