| With the development of mobile communication technologies and the advancement of the science technologies, the requirement of wireless terminal for antenna is strict more and more. For example, small volume, light weight, wideband and so on. Nowadays, the antennas for mobile communication applications can be divided into two categories, one is external antenna, including quarter-wavelength whip antenna, quarter-wavelength telescopic antenna (combinations of oscillator helical antenna), helical antenna, etc., the other is internal antenna, including microstrip slot antenna, microstrip patch antenna, polyrod antenna, cavity-backed radiator antenna, ferrite antenna, etc. In a variety of internal antennas, microstrip antenna is widely used for it's a good many advantages, for instance, low profile, light weight, easy to co-type with carriers, feeding network can be printed together with antennas, suitable for the production of printed circuit technology, convenient for circular polarization, dual polarization, two-band work and so on.However, in some applications of communication technologies, such as mobile communications, television, FM broadcast, radar, satellite and the like, the frequency channels are usually lower band (Very High Frequency: 30~300MHz; Ultra High Frequency: 0.3~3GHz), so the dimension of conventional half-wave antennas are too big to use. To satisfy the requirement of some especially frequency channel applications, research and produce compact microstrip antenna is shoulder heavy responsibilities. On the other hand, most of the conventional microstrip antennas are resonance antenna, relative bandwidth of them are narrow, the bandwidth with general design is less than 3 percent. Moreover, the lower the operating frequency is, the smaller the bandwidth is. The defect such as narrow bandwidth significantly restricts the application of microstrip antennas. Furthermore, compact and broadband microstrip patch antenna is one of the important types of internal antenna for mobile terminal, so it is significant to design compact and broadband microstrip antenna, it is also the hotspot and difficulty of modern antenna design.This paper research on the miniaturization technology for microstrip antenna which is shorting pins loaded. And base on a large number of simulation results, the author summarizes the regularity between all relevant parameters of shorting pins and performances of antennas. On the basis of a comprehensive master of this miniaturization technology, the author designs a compact and broadband microstrip antenna. Therefore, research and design compact microstrip antenna of excellent performance is also the main content of this paper.In this paper, the first part of the core content is base on a modal of traditional rectangular microstrip antenna which is loaded with shorting pins, summarize the performance of this compact technology through the contrast and analysis of a great deal of results which are emulated by HFSS. Now summarized briefly as follows:1. It is proved that microstrip antenna which is loaded with a shorting pin will appear a new resonant frequency, and the new frequency is lower than previous frequency. Furthermore, the previous frequency has no significant change. The new frequency can be utilized to reduce the dimension of microstrip antennas effective. 2. Through the research on the position of shorting pins, it is certified that the resonant frequency is lowest when shorting pin is loaded on the edge of patch, so it is most effective for miniaturized antenna.3. The rectangular microstrip antenna with one shorting pin can realize impedance match by adjust feeding point, then the frequency decreased form 1.63GHz to 0.53GHz, the new frequency is 32% of previous frequency, it is sufficient to prove that loading with shorting pins is an effective method to realize miniaturization. But unavoidably, the distance between shorting pin and coax probe is too small to produce.4. This paper also explain that although shorting pins loading is a useful method to diminution the dimension of antennas, it also have negative effects to the radiation characteristic, then solution approaches are presentation in this paper.5. Through researching on the influence of shorting pins'number on the performance of antennas, the author learns that the relation between number of shorting pins and resonant frequency is direct proportion. On the other hand, the larger the number of shorting pins, the smaller the input impedance is, thus the feed point need to be moved towards the shorting pins.6. Summarize the relationship between the distance of shorting pins and the frequency of operation, the author finds when the distance increase, input impedance augment, and the operation frequency increased first and then decreased, it is symmetrical distribution.7. At the end of the paper, the author explored the effects of other parameters of shorting pins to antenna characteristics. According to the results of emulation and analysis of theory, following rules are reached: when the radius of shorting pin increases, resonant frequency of antenna will increase, and the input impedance of antenna will decrease. Moreover, the effect of thickness of substrate on resonant frequency is small, and as the increase of thickness of substrate, the bandwidth and inductive effect increase. However, the increase of thickness will add to the weight and size of the antenna.In this paper, the main work and innovation are:1. Introduce the theoretical knowledge about microstrip antenna, summarize the analytical method for microstrip antenna; Study the existing miniaturized technologies, and introduce their principles, applications and merits and faults in detail.2. Research on the theory principle of shorting pins loading to realize antenna miniaturization, analyze the relationship between the parameters of shorting pins and characteristics of microstrip antenna detailed, and summarize the lows of them, thus the technology has been mastered overall.3. Base on the research of miniaturized method, the author designs a new type compact and broadband microstrip antenna which is applied for DCS1800 frequency channel. In the paper, the author introduces the design ideas and research manners, and build the physical model of propose antenna. The results of emulation certify what the paper research on is rational and feasible. The results of this kind of physical model and principle analysis are valuable to design new type microstrip antenna in the future. Although microstrip antennas have widely applications, the technology is still immature. It needs further development in many aspects, such as the materials of substrate, multi-polarization technology, fractal technology, computer aided design and computer aided manufacturing etc. Along with the advancement of science and technology, the people lucubrate on microstrip antennas, the technologies of design and manufacture of microstrip antennas will become more and more perfect. |
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