Abstract-This study focuses on the user influence on a MIMO antenna system in a smart phone form factor. The antenna system is designed to have a low coupling and correlation between its two antennas. The study is based on time-domain simulations of the antenna system in free space and with a head and hand phantom using a commercially available Finite Element Method solver. The MIMO parameters are evaluated with three different channel models.A static grip only gives one case of the user effect so the hand phantom is modified with a moving finger that is swept across the backplane of the phone. Based on the results of the study it is concluded that the placement of the index finger has a significant effect on the simulated antenna system. For certain finger placements the mismatch loss and absorption loss both change more than 5 dB.Overall the antenna system shows good MIMO performance in free space but suffers under the influence of the user. Especially the diversity antenna is heavily detuned and gives a total efficiency of -19.1 dB worst case compared to -1.9 dB in free space. The branch power ratio is increased by the user while the envelope correlation is decreased by the user.
Modern smart phones require antenna systems that can deal with an ever-growing number of bands. This study compares two different approaches to the coverage of large bandwidths: Wide-band (WB) antennas covering a whole band at once and tunable narrow-band (NB) antennas covering only one channel at a time but tunable to all channels within the band of interest. To investigate the effect of antenna placement the antennas are placed both at the top and the bottom of the phone. All antenna configurations are simulated in talk position with a head and hand included. The hand is constructed with a movable index finger and the index finger is swept at 6 positions on the backside of the phone. The study shows that WB antennas detune a lot more than NB antennas and that top-mounted antennas are experiencing more than 6 dB higher losses than bottom-mounted antennas. It is proposed to expand this study with more antenna types and placements as both of these parameters are known to influence the immunity to the user. It is also proposed to compare the simulation results to measurements to increase the confidence in the results.
Abstract-In this contribution, we are proposing a compact design for an implementation of a two element MIMO antenna destined for LTE smart phones. The antennas are collocated at one end of the PCB to minimize antenna volume. Each element is dual-band and frequency reconfigurable using tunable capacitors. The MIMO performance is investigated in two different channel models through efficiency, branch power imbalance and envelope correlation. The proposed antennas have acceptable levels of isolation between them, even in the low-bands, while having a good efficiency. Furthermore, the correlation coefficient is controlled by manipulating the ground currents between the antennas using a tunable capacitor. Nonetheless, using this mechanism to control the coupling between the antennas, the total efficiency is affected.
Abstract-Antenna mismatch and crosstalk are recurring issues in telecommunications. For electrically small antenna systems these are very hard to measure without affecting the radiation performance of the system and, consequently, the measurement itself. Electrically small antennas are found in many applications ranging from consumer electronics to industrial systems. We propose a radically new approach to characterize crosstalk and mismatch based on vector network analysis. By miniaturizing the network analyzer it can be integrated in the system under test eliminating the need for cables leaving the system. The tiny integrated network analyzer (TINA) is a standalone Arduino based measurement system utilizing the transmit signal of the system under test as its reference. It features a power meter with triggering ability, on-board memory, USB and easy extendibility with general purpose I/O. The accuracy and repeatability of the proposed system is documented through the repeatability of the calibration. To showcase the capabilities of the system, a measurement is done on a modified smart phone with the system inside. These early results show great promise for miniaturized network analysis. With the advances in software defined radio we can expect much more flexible and advanced integrated network analyzers in the coming years.
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