Andres Alayon Glazunov

Reduction of the Envelope Correlation Coefficient With Improved Total Efficiency for Mobile LTE MIMO Antenna Arrays: Mutual Scattering Mode

A mutual scattering mode is introduced in this paper. Utilizing this mode, the correlation of a lossy long-term evolution (LTE) multiple-input and multiple-output (MIMO) antenna array can be reduced efficiently, even down to zero, by increasing the Q factors of the MIMO antenna elements. In practice, the Q factors can be straight forwardly tuned through different input impedance matching. The zero correlation occurs at a Q factor higher than that resulting from the conjugate input impedance matching. On one hand, if the inter-element distance is larger than a certain distance (what we denominate as the Critical Distance), the total efficiency can also be improved in addition to reducing the correlation. On the other hand, when the inter-element distance is less than the critical distance, a reference MIMO antenna with high correlation and high total efficiency is obtained. This antenna can well be proposed for over-the-air (OTA) measurement applications. The introduced scattering mode is investigated for dual monopoles on a large lossy ground plane and for various mobile terminal MIMO antenna designs. A wideband MIMO antenna, with multiple resonances, covering the band 746-870 MHz is proposed with the envelope correlation coefficient and total efficiency less than 0.5 and higher than 50% (-3 dB), respectively. Measurements and simulations agree well for all the fabricated prototypes. The envelope correlations and the multiplexing efficiencies of the prototypes are also investigated in propagation channels with Gaussian distributed angle of arrivals.

Spherical Vector Wave Expansion of Gaussian Electromagnetic Fields for Antenna-Channel Interaction Analysis

In this paper, we introduce an approach to analyze the interaction between antennas and the propagation channel. We study both the antennas and the propagation channel by means of the spherical vector wave mode expansion of the electromagnetic field. Then we use the expansion coefficients to study some properties of general antennas in those fields by means of the antenna scattering matrix. The focus is on the spatio-polar characterization of antennas, channels and their interactions. We provide closed form expressions for the covariance of the field multimodes as function of the power angle spectrum (PAS) and the channel cross-polarization ratio (XPR). A new interpretation of the mean effective gains (MEG) of antennas is also provided. The maximum MEG is obtained by conjugate mode matching between the antennas and the channel; we also prove the (intuitive) results that the optimum decorrelation of the antenna signals is obtained by the excitation of orthogonal spherical vector modes.

Theoretical analysis of mean effective gain of mobile terminal antennas in Ricean channels

The mean effective gain (MEG) for Rice distributed signals impinging at the terminal receiver antenna is presented. Numerical results are presented for three different angular probability distributions of impinging waves. Finally, it is shown that contrary to the Rayleigh channels in Ricean channels there is no inclination angle at which the MEG of the half-wave dipole antenna remains constant regardless the crosspolarization ratio (XPR) of the channel.

Interpreting the Total Isotropic Sensitivity and Diversity Gain of LTE-Enabled Wireless Devices From Over-the-Air Throughput Measurements in Reverberation Chambers

The characterization of the performance of wireless devices is key to developing new RF products conforming to the latest communications protocols. Traditionally, communication performance tests have focused on the RF performance of the tested devices, e.g., smart phones, pads, laptops, and so on. In particular, the focus has shifted from conducted (i.e., cabled) measurements to more realistic over-the-air (OTA) characterization of the RF performance of these devices in transmit or receive mode. For example, the receiver performance of 2G and 3G wireless devices can be measured in terms of the total isotropic sensitivity (TIS) that depends on the antenna and the receiver parts of a wireless device. These measurements can be performed in a reverberation chamber setup. However, standard TIS measurements can be time-consuming and do not reflect the actual performance gains of multiple-input multiple-output antenna systems operating over orthogonal frequency division multiplexing channels, such as those encountered in 4G long-term evolution (LTE) systems. Therefore, in order to meet both time and cost efficiency requirements, we propose here a new method to determine the TIS, as well as the diversity performance, of an LTE device based on throughput measurements. The proposed method shows that the TIS of an LTE device is characterized much faster directly from OTA throughput measurements than from standard TIS measurements and with excellent accuracy.

Cost-effective measurement setups for testing wireless communication to vehicles in reverberation chambers and anechoic chambers

Autonomous (self-driving) cars will in a few years become a reality, driven by safety aspects. This will be made possible by reliable and secure wireless connections to the car via the wireless network, and directly from other vehicles in the close vicinity. Thereby OTA-testing becomes a big issue, both in multipath and Line-Of-Sight (LOS). The present paper proposes two compact and cost-effective test chambers that take account of the two limiting environments known as Rich Isotropic Multipath (RIMP) and Random-LOS. The randomness of the latter is associated with the unknown and arbitrarily distributed angle of arrival of the LOS in the horizontal plane, sometimes also having an unknown polarization, which thereby also become random.

Comparison of MEG and TRPG of practical antennas

In this paper two figures of merit of UE antenna performance are compared, the mean effective gain (MEG) and the total radiated power gain (TRPG). The ratio between these magnitudes has been evaluated first theoretically and later from measurements of four different handsets in the GSM, AMPS bands. In the evaluation different power angular distribution models were assumed. It is also shown that in practice an estimate of MEG could be obtained from the TRPG.

Building shielding loss measurements and modelling at the 5 GHz band in office building areas

This paper presents narrowband path loss measurements carried out at the 5.1 GHz band. The focus has been on building-shielding loss in office-building areas. Both azimuth and elevation dependence have been studied. The measurement campaign was performed in a multi-storey building on three different floors in an indoor office environment. A helicopter was used to simulate a mobile satellite system feeder link position in orbit. A differential GPS receiver was used to track the helicopter trajectory. The obtained measurement data is compared to results predicted by a model showing a good agreement between them. The measured shielding loss varied in the interval from 10 to 45 dB with a harmonic average of 19.1 dB for the elevation measurements and 22.3 dB for the azimuth measurements.

On the Physical Limitations of the Interaction of a Spherical Aperture and a Random Field

This paper derives physical limitations on the interactions of antennas exciting TM or TE modes (but not both) and wireless propagation channels. The derivation is based on the spherical vector wave expansion of the electromagnetic field outside a sphere circumscribing the antennas. The result is an extension of the seminal work of Chu on the classical limitations on maximum antenna gain and radiation Q . Rather than maximizing antenna gain in a single direction we obtain physical limitations on the antenna gain pattern, which is directly translated to more condensed parameters, i.e., the instantaneous effective gain Gi and the mean effective gain Ge if instantaneous realizations or correlation statistics of the expansion coefficients of the electromagnetic field are known, respectively. The obtained limitations are on the maximum of Gi/Q and Ge/Q, which establish a trade-off between link gain and Q .

Building-shielding loss modelling

An approach devised for shielding loss calculation and a model derived from it are outlined. The model handles a building of arbitrary dimensions occupied by wireless terminals with a given probability distribution and illuminated by a satellite. Two models for the probability distribution of the wireless terminals within a building are considered: uniform over the whole floor at a given height above it and uniform at some distance from the exterior wall also at a given height from the floor. Analytical expressions for the building shielding loss as averaged over a building of arbitrary dimensions as a function of the elevation angle and the building parameters, such as building dimensions, attenuation of walls, floors etc., are given. Numerical results for some relevant building models such as office-buildings, factories, simple houses etc., are also presented.

Statistical analysis of measured short-term impulse response functions of 1.88 GHz radio channels in Stockholm with corresponding channel model

A statistical analysis of amplitudes corresponding to multipath components in outdoor (urban/suburban) channels is presented. The study is based on short-term complex impulse response measurements conducted in Stockholm at 1.88 GHz carrier frequency with 5 MHz bandwidth. The actual investigations show that the Rice distribution gives the best fitting in the Kramer-von-Mises sense. Further it is shown that in average the strongest tap fades less than the other taps in the impulse response. A global average model was devised for the power delay profile and corresponding Rice K-factor.