| Traditionally,the term "ultra-wideband"(UWB) has been associated with terms such as impulse, the baseband, time-domain, non-sinusoidal, orthogonal function and large-relative-bandwidth radio/radar. The basic feature of the UWB systems will be the occupancy of an extremely wide operating bandwidth, compared to conventional radios,due to their use of impulse signals. Since 2002, several countries released the spectra of below 900 MHz and 3.1-10.6 GHz bands for the unlicensed use of UWB systems.Commercial applications include imaging systems and vehicular radar systems, as well as communication and measurement systems。However,considering the interference of other existing communication bands, such as WLAN,WIMAX and satellite communication system, in order to design a more practical UWB antenna, which includes several stop-bands is one of the hot topics. But the current ultra wideband antennas with band notched characteristics are usually with large volume, single stop-band, and the signal suppression ability is not strong enough. For this phenomenon,this paper designed three kinds of ultra wideband antennas with several stop-bands and high performance. Taking into account the high integration of modern communication equipment, this paper also studied the dual band antenna. The research contents of this paper are as follows:In the first part, the design of a UWB antenna with dual stop-bands is proposed..The main design method: by adding radiation branches with different lengths at the back side of the radiation patch, we can get two stop-bands which covers 3.2-3.7GHz and 5.8-6.1 GHz,by adding another branches, we can get an additional Bluetooth band.The radiation patch is a ladder shaped structure, which improves the high frequency characteristics of the antenna. The maximum return loss of the two stop-bands are up to-0.2dB and -1.3dB, respectively, which has a strong ability to suppress the stop-band signal.The second part, the integrated use of stop-band technology. Through etching annular groove in the radiation patch, adding resonators near the feed line, Successfully,we get the planar monopole UWB antenna with four stop-bands which has the advantage of a simple structure, low cost, The influence of various parameters on the performance of the antenna is discussed in detail。And the maximum value of the return loss of each stop band is above -3dB。Compared with the antenna in the previous paper it can be widely used in antenna communication system.The third part is based on the design of the ACS-fed UWB antenna operating from 2.8GHz-11GHz. By etching slots on the antenna structure of the ground, feed-line, and radiation unit we can obtain stop-bands in the WIMAX, WLAN and satellite communication frequency band. The current distribution of the antenna in each frequency band is given, and the working principle of the antenna is discussed。 The antenna volume is only 30*10mm~2, compared with the previous three band stop ultra wideband antennas, the volume has been greatly reduced which is beneficial to the miniaturization of antenna.The fourth part, the use of the ACS-feed structure, The resonant frequency of the antenna can be changed effectively by etching slots on the antenna. The dual frequency characteristic of the antenna is realized by adding resonant element method. A compact dual band antenna capable of working in both WLAN and WIMAX bands is successfully designed。The directional pattern of the antenna is given, and the reasons of the deviation of the resonance frequency shift is explained by analyzing the current distribution... |
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