With the rapid growth and development of the mobile communication technologies in recent years, many mobile communication technologies appeared one after another, of particu- lar concern is 3GPP long term evolution (LTE). TD-LTE is growing rapidly in China and is also widely considered in the forth generation (4G) mobile communication now. MIMO technology, which utilizes multiple antenna to improve spectrum e-ciency and increase the system channel capacity, is one of the 4G key technologies. In this paper a MIMO antenna, operating on TD-LTE frequency band for TD-LTE mobile ter- minal is designed. The proposed MIMO antenna consists of two modifled IFA structures has the advantage of compact structure and multiband for 4G handheld devices. The antenna designed to cover the TD-LTE frequency band of 1880 i1900MHz and 2575{2635MHz for China Mobile. The simulated and test results show that the isolation and S11 parameters of the proposed MIMO antenna can meet TD-LTE mobile communication requirements. 1. INTRODUCTION The 4th generation in the wireless evolution is called the Long Term Evolution (LTE) which will provide higher peak data rates, higher spectral e-ciency and lower latency taking advantage of the latest enabling technologies such as Orthogonal Frequency Division Multiple Access (OFDMA), Adaptive modulation and coding (AMC) and Multiple-Input Multiple-Output (MIMO) technolo- gies. The 1.8GHz and 2.6GHz band is used for China Mobile's LTE systems in mainland China. Due to the small size of LTE mobile terminal, the design of Multiple-Input Multiple-Output (MIMO) antenna with broadband or multiband on small handsets is a real challenge. And due to the integration of multiple antennas on a single portable device with very limited space, mutual coupling between multiple antennas is severe, and the MIMO antenna for mobile terminal systems with high isolation is of great importance to bring 4G capabilities to reality. Many printed MIMO antennas have been discussed in literature recently. In (1), a compact planar MIMO antenna system of four elements is proposed for the whole 2.4-GHz WLAN band. Two types of antenna elements printed on difierent sides of the substrate are used in the structure for better isolation performance. In addition, a series of slits etched in the ground plane is proposed to improve the mutual coupling. In (2), a modifled PIFA antenna by adding a proper chip capacitor was designed to enhance the lower band and by adding a shorted strip or forming a coupled section to enhance the upper band. In (3), by adding the two parasitic monopoles, the mutual coupling is greatly improved, meanwhile, the bandwidth increases somewhat. In (4), a penta-band CRLH-based antenna was designed and integrated into a cellular handset. The measured results demonstrated that the proposed CRLH-based antenna had superior performance and smaller size compared to other conventional antenna designs. In this article, we proposed a modifled IFA antenna printed on one top layer of a 0.6mm thick with the FR4 substrate and the dielectric constant of 4.5. The antenna was designed to cover the low band and upper band of TD-LTE for mobile terminals. 2. ANTENNA DESIGN
A low-profile radio frequency identification (RFID) tag antenna is proposed with a compact size of 45 ×45 mm 2 and circular polarization (CP) for metallic surfaces. A star-shaped slot is etched onto the antenna for the CP and antenna size reduction. A terminal-grounded L-shaped feedline is embedded in the etched slot to efficiently excite the wideband CP mode, complexly match the tag-antenna impedance, and further reduce the antenna size. The embedded feed structure also helps achieve a relatively higher gain, resulting in a longer reading range. The proposed antenna can cover the impedance bandwidth of 60 MHz (from 880 to 940 MHz) as well as the 3-dB CP bandwidth of 12 MHz (from 905 to 917 MHz). Further results demonstrate that the proposed tag antenna provides a stable reading range when mounted on metal plates of various sizes.
In this paper, an-ultra-high frequency (UHF) passive broadband radio frequency identification (RFID) Tag Antenna with a novel T-matching network is presented. By slightly tuned the arm lengths of the T-matching network, the impedance matching between the antenna and the chip and a broad impedance bandwidth is obtained. Thanks to the bent radiating element, the size reduction of the proposed antenna is realized. The bandwidth (S11 l -20 dB) and the corresponding 3 dB PRC bandwidth of the proposed antenna are 133MHz (835-968 MHz) and 88MHz (882-970 MHz) respectively, which means that both bandwidths are wide enough to cover the whole global UHF RFID frequency band. In the simulated results, a smooth and stable gain curve between 0.04 dBi to 1.86 dBi is found throughout the entire operating frequency band, and a gain of 1.38 dBi is obtained at the desired operating frequency point (915 MHz). In conclusion, the designed antenna owns the advantages of low-profile, compact size (56×56mm2), low cost and stable gain. Based on the simple structure, the designed tag antenna can be easily manufacture and widely used in practical applications.
A passive radio frequency identiflcation (RFID) tag antenna with circular polar- ization (CP) radiation is proposed to operate at 902{928MHz and mount on metallic surfaces. A U-shaped terminal short-circuited feedline welded to a tag-chip is embedded in a rectangular slot to achieve a coupled feeding and a good impedance matching. By employing two truncated corners and two L-shaped slots with unequal length on the patch, a good left-hand circular polarization (LHCP) and compact size are obtained. The measured impedance bandwidth of the antenna is 85MHz (875{960MHz), while the simulated 3-dB CP bandwidth is 6MHz (912{ 918MHz). The proposed tag antenna shows reasonable read ranges when mounted on the metal plate in the following experiment.
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