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 novel compact dual-band power divider integrated with filtering responses is presented in this paper. The proposed circuit utilizes two sets of resonators. By controlling these resonators, dual-band operation can be realized and the pass bands can be tuned independently. Furthermore, a resistor is connected between the two open ends of the feed line to obtain good isolations at two bands. To verify the proposed idea, a filtering power divider with the operating frequencies of 2.4 and 5.8 GHz is designed. Good power division and dual-bandpass responses are obtained. The total size of the circuit is 0.29λ g × 0.29λ g , where λ g is the guided wavelength of 2.4 GHz.
This paper presents a novel transmission line which has a constant phase shifter over a wide band, referenced to a uniform transmission line. The novel transmission line is loaded with lumped element. Compared with the conventional coupled line phase shifter, the configuration shows good performance with simplicity in both design and fabrication. And the use of lumped elements make the size more compact, especially for low band phase shifter design. To verify the configuration, a 90 degree phase shifter using a transmission line loaded with a capacitor and an inductor is designed. Excellent performance is achieved with small insertion loss and phase deviation over a bandwidth of 116%. The operating frequency ranges from 824 MHz to 2690 MHz, covering the bands of mobile communication 2G, 3G and 4G.
As wireless communication develop rapidly in recent years, mobile terminals are smaller and more integrated. Circuits, such as Bluetooth, WiFi, 3G and 4G, are designed in one terminal, these make antenna should be multiband to meet the system's requirement. Then, how to design a multiband antenna with a limited space is a key problem for mobile terminal device. In this letter, we proposed a new antenna structure to realize multiband properties. In order to get the antenna's multiband properties, several branches were used. Coupling structures were used to make a compact antenna model. The radiation structure was connected to the antenna ground by a shunting inductor that can improve the antenna performance. The antenna was simulated by CST. Both results from simulation showed that the designed antenna can meet the requirements of 4G mobile terminals.
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