| Wireless body area network(WBAN) is a body-centric wireless network, and it has broad application prospects in military and medical treatment. Ultra wideband(UWB) technology has wide applications because it can share frequency band with the existing spectrum resources, and it is also one of the best candidate technology to realize the WBAN. The design of UWB antenna is a new challenge to the traditional theory of antenna design. It can better meet the needs of WBAN when the antenna is worn in human body for wireless data transmission. The UWB antenna and wearable antenna in WBAN are mainly studied in this dissertation, the equivalent circuit, transfer function and time domain waveforms are considered in UWB antenna analysis. Electromagnetic band gap(EBG) structure is loaded in wearable antenna in order to reduce the electromagnetic radiation on the human body, and the characteristics of wearable antenna in bending and near the human body are also studied. The main research contents and results are as follows:1. Three UWB antennas are studied and designedA miniaturization printed circular slot UWB antenna is presented by the half-cutting method according to the current distribution, a nd the scaling principle. The antenna has a size conduction of 0.125 times as compared with the original structure. Magnitude of the measured transfer function is flat from 5.5 GHz to 10.6 GHz, the phase is liner, and the fidelity factor in xz plane is more than 0.9750, which are suitable for the transmission of impulse signals.According to the theory of microwave transmission line, a notched UWB antenna with quarter wavelength shorting resonator is presented based on the antenna with half wavelength opening resonator. When the radiation characteristics remain almost unchanged, the antenna can improve the voltage standing wave ratio and decrease the gain value in the stop band, which has a better filtering effect.A dual band- notched U-shaped monopole UWB antenna is proposed by the method of slotting on the radiating element and the ground plane. According to the distribution of surface current, in the analysis of transmission line theory, parallel connection of terminal open transmission line and series connection of terminal short circuit transmission line are used to analyze the 3.5GHz and 5.5GHz notched characteristics. The equivalent circuit of the RLC resonant network is consistent with the structure of the antenna input impedance, which verifies the correctness of the equivalent circuit.2. Two EBG structures are studied and designedBased on analysis of rectangular patch electromagnetic band gap structure, a rectangular ring shaped single frequency electromagnetic band gap structure is presented by cutting holes in the metal layer. The structure has the characteristics of easy fabrication, and it is suitable for wearable applications. On this basis, a rectangular ring shaped double frequency electromagnetic band gap structure is designed. The parameters of each freque ncy band can be adjusted by selecting reasonable parameters, and it has little influence on the other frequency band. By analyzing the surface current distribution and reflection phase curves, the parameters of these two kinds of electromagnetic band gap s tructures are optimized, and the results of the suspended microstrip line method can meet the design requirements.3. Two wearable antennas are studied and designedOn the base of circular slot UWB antenna, a wearable circular slot antenna for 2.4GHz WLAN band is presented. In order to reduce the electromagnetic radiation on the human body, the rectangular ring shaped single frequency electromagnetic band gap structure is used in antenna. The calculated SAR values decreased to 0.554 W/kg in 1g standard and 0.23 W/kg in 10 g standard, which meet the standards used in the United States and Europe. The advantage of wearable circular slot antenna is wide band width, so it is easier to cover required frequency band when the antenna is bending. The disadvantage is that the resonant frequency shifting with the antenna bending, and it has poor stability.A wearable dual band planar inverted F antenna for 2.4GHz/5.8GHz WLAN is proposed. The two working band can be realized by adjusting the length of two resonant unit, and it has little effect with each other. After loading the electromagnetic band gap structure, the unidirectional radiation characteristic is appeared in radiation pattern, the antenna gain is increased in the working frequency band, and the electromagnetic radiation to the human body also meets the requirements. The advantage of the wearable dual band planar inverted F antenna is very good stability, and the effect of antenna bending on the resonant frequency is small. The disadvantage is that the bandwidth is narrow.In this dissertation, the UWB antenna has the characteristics of plane and miniaturization, and it is easy to be integrated with microwave system; the electromagnetic radiation on the human body of wearable antenna meets the requirement. The wearable antenna has features of flexibility and comfort, and it is easy to be integrated into the clothes. The work of this dissertation has an important meaning for the practical application of antennas in wireless body area networks.
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