| With the rapid development radio communication system toward integration, multi-function, miniaturization, the antenna as an entrance and exit for these systems will be forced to become miniaturized,multi-frequency and wide bandwidth. In several years, met-materials have begun to attract people’s attention in physics and electromagnetic field due to its peculiar properties. Compared to the traditional left-handed materials, the composite right/left-handed transmission line (CRLH-TL) which is the left-handed materials’micro-strip realization type is widely used to open up a new mind in radio frequency/microwave devices designed due to continuity of structure, lower loss and wider bandwidth. So this paper mainly studies the miniaturized and multiple frequency antennas based on composite right hand transmission line.Firstly, the research background and significance about the antenna’s miniaturization, multi-frequency based on the CRLH-TL and research situation of met-materials in microwave/radio frequency devices design especially in antenna deign have been introduced briefly. Then the theories on the left-handed materials transmission line theory, magnetic properties and composite right-hand man of the transmission line theory, especially the basic principles of zero-order resonator have been studied in detail.Secondly, after summarizing several common techniques of miniaturized antenna, a miniaturized antenna based on ENG-TL has been designed. The designed antenna comprises of one unit cell of ENG-TL. In order to achieve the bandwidth to cover2.5-2.69GHz, a strip is inserted connected between the metallic patch and the ACPW (asymmetric coplanar waveguide) ground plane to obtain a new resonant frequency at2.53GHz. The bandwidth enhancement of designed antenna can be obtained when the zeroth-order resonant frequency and the resonant frequency at2.53GHz are merging together. A prototype designed on F4BM350substrate with dielectric constant3.5occupies an overall size of15x22x0.8mm3. The measured result shows that the operating bandwidth with10dB return loss is about330MHz (2.49-3.0GHz). The antenna has a small size, compact structure and stable radiation characteristics, which are suitable for WiMAX/2.5GHz application.Then, after summarizing several common techniques of multi-frequency antenna, a triple-band antenna based on met-material loaded technology has been designed. The designed antenna comprises of a rectangle patch radiating element, a strip, and a CSRR (ComplementarySplit Ring Resonator, CSRR-shaped slot. By embedding a trip connected between the rectangle patch and an ACPW ground plane, an epsilon negative transmission-line (ENG-TL) metamaterial loaded is achieved to obtain a zeroth-order mode. In order to cover WiMAX(3.4-3.69GHz) band, a CSRR-shaped slot in the patch is embedded. A prototype designed on ArlonAR350(tm) substrate with dielectric constant3.5occupies an overall size of14.5x25x0.8mm3. The measured results show that the proposed antenna operates over the frequency ranges of2.35-2.61GHz,3.38—4.01GHz and4.25-6.65GHz. The antenna has compact structure, a small size and wide bandwidth, which are suitable for WLAN2.45/5.3/5.8GHz and WiMAX3.5/5.5GHz application.Lastly, after summarizing several common techniques of frequency tunable antenna, we combined the frequency tunable technology and the zeroth-order resonant theory based on CRLH-TL, one frequency tunable miniaturized antenna based on the CRLH-TL is designed. The antenna’s size is only13x14x0.8mm3, the simulated results show that the resonant frequency can be tuned about890MHz, the radiation characteristic is stable when the value of variable capacitance diode changes. |
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