論文研討 : MinSeok Han and Jaehoon Choi “Compact Multiband MIMO Antenna for Next Generation USB Dongle Application” 報告人 : 碩研電子一甲 MA 蘇暐倫

研究方向 : In this paper, we propose a compact printed strip MIMO antenna with an embedded chip inductor for next generation USB dongle application. 設計方法 : The proposed MIMO antenna consists of a chip-inductor- embedded longer radiating strip and a shorter radiating strip. Both the longer and shorter strips can also be incorporated close to each other to have a compact structure. The embedded chip inductor contributes additional inductance to compensate for the increased capacitance resulting from the shortened radiating strip.

The geometry of the proposed MIMO antenna embedded with a chip inductor multiband MIMO antenna for 4G system is shown in Fig. 1. Two same elements are placed at the two corners of top edge of a FR4 (εr = 4.4) substrate having the volume of 25 mm× 66 mm× 0.8 mm, which simulates the ground plane of a practical USB dongle. Figure 1. Geometry of the proposed MIMO antenna

The radiating portion of the antenna is a simple two- strip PIFA. The shorter strip has a length of about 12 mm, which is about 0.1 wavelength at about 2.0 GHz and can easily generate a wide resonant mode to cover WCDMA operation in the 2.05 GHz band. The longer strip with an embedded chip inductor of 15 nH has a total length of about 34 mm, which is about 0.08 wavelength at about 0.77 GHz. Owing to the embedded chip inductor, the resonant mode contributed by the longer strip can be effectively shifted to lower frequencies of about 0.77 GHz, from an about 1.3 GHz. Effects of the two radiating strips of the proposed MIMO antenna are analyzed in Fig. 2. It is clear that the antenna’s lower and upper bands are contributed by the longer and shorter strips, respectively.

Figure 2. S-parameter characteristics for the proposed MIMO antenna Simulation was carried out with the aid of the commercially available simulation software MWS [6] to optimize the geometric parameters of the proposed antenna. From the measured S-parameter characteristics, the two antenna elements have very narrow bandwidth of 30 MHz at the LTE band 13 and sufficient bandwidth at the WCDMA/WiBro band, respectively. The additional study is required to widen the bandwidth at the LTE band 13 and to enhance antenna gains and radiation efficiencies at LTE band 13.

Although MIMO antenna elements usually have different directivity for each element, the radiation patterns of the designed antennas resemble to each other.

From the H (zx)-plane patterns, it is confirmed that monopole-like radiation patterns at three frequencies are obtained, and omni-directional total power radiation is generally seen, which is advantageous for practical applications. Figure 3. Measured radiation patterns of the proposed multiband MIMO antennas

Table 1. Measured antenna gains and antenna efficiencies The measured peak gains of two antenna elements are dBi and dBi at the LTE band 13, 3.5 dBi and 2.9 dBi at the WCDMA band and 3.4 dBi and 3.2 dBi at the WiBro band, respectively.

In this paper, a compact printed strip MIMO antenna with an embedded chip inductor for LTE/WCDMA/WiBro applications was proposed. The proposed MIMO antenna consists of a simple two-strip monopole and embedded chip inductor. The antenna’s lower and upper bands are contributed by the longer and shorter strips, respectively. The fabricated antenna has the isolation of about -18 dB at the lower band and lower than -12 dB at the higher band. The measured peak gains of two antenna elements are dBi and dBi at the LTE band 13, 3.8 dBi and 3.5 dBi at the WCDMA band and 3.4 dBi and 3.2 dBi at the WiBro band, respectively. The simulated and measured results show that the proposed multiband MIMO antenna could be a good candidate for 4G mobile systems.

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