Ahmed Hussain

Threshold Receiver Model for Throughput of Wireless Devices With MIMO and Frequency Diversity Measured in Reverberation Chamber

We present a simple theoretical model for the throughput data rate of a wireless LTE device including the improvements of data rate due to diversity in frequency (OFDM) and spatial domains (MIMO) under frequency selective fading. The model is based on defining an ideal threshold receiver for the line-of-sight (LOS) case, corresponding to reception with advanced error-correcting codes. The theoretical throughput model is in agreement with measurements in a reverberation chamber of a commercial LTE device for the 1 × 2 SIMO case, both regarding diversity and MIMO array gains, and it can therefore be used to complement measured results in evaluation of performance of LTE devices.

Wideband Compact 4-Port Dual Polarized Self-Grounded Bowtie Antenna

We present a dual-polarized self-grounded bowtie antenna. The antenna is mechanically simple and wideband. One of the characteristics is its flexibility: it can be used either as a 4-port antenna in multiple-input-multiple-output (MIMO) systems or as a directional 2-port dual-polarized antenna in radar or sensor systems. The latter application requires a balun. The 4-petal geometry of the antenna has been optimized for the best matching to 50 Ω coax over 1.5-3 GHz. Both simulated and measured results are presented to verify the design. The antenna radiates over parts of the bandwidth similar to four Huygens source, one from each petal, each having directivity close to 4.8 dBi.

A maternal diet of fatty fish reduces body fat of offspring compared with a maternal diet of beef and a post-weaning diet of fish improves insulin sensitivity and lipid profile in adult C57BL/6 male mice.

The maternal diet during pregnancy and lactation may affect the long‐term health of the offspring. Our aim was to study how a fish or meat diet perinatal and after weaning affects body composition, insulin sensitivity and the profile of n‐3 and n‐6 polyunsaturated fatty acids (PUFAs) in breast milk, fat depots, skeletal muscle and liver in male adult mice offspring.

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.

A New Compact Wideband MIMO Antenna—The Double-Sided Tapered Self-Grounded Monopole Array

We present a new compact wideband multiple input multiple output (MIMO) antenna-the double-sided 4-port arm-tapered self-grounded monopole array, briefly referred to as the butterfly antenna, in the communication. The antenna is very compact with low correlation between ports and high diversity gain. The genetic algorithm optimization scheme has been employed in the design. Simulation results have been verified against measurements. The measured reflection coefficients at all ports are below -7 dB over 0.5-9 GHz and below -4.5 dB over 0.4-0.5 GHz and 9-15 GHz. The measured correlation coefficients are below 0.4 over 0.4-15 GHz and lower than 0.1 in most of the frequency band. This new MIMO antenna is developed as a transmit antenna in reverberation chambers, and we believe that it will find more applications in other systems, such as micro base station antennas in wireless communication systems.

Measurement of Radiation Efficiency of Multiport Antennas With Feeding Network Corrections

Multiport antennas are widely used and often integrated with active components, such as low noise amplifiers, in antenna systems. It is important to verify and evaluate the radiation efficiency of a multiport antenna before being integrated in the system. When the radiation efficiency of a multiport antenna is measured, a multiport feeding network is always needed in order to provide the same antenna excitation as it is during its operation after being integrated in the system. This letter addresses how to measure the radiation efficiency of a multiport antenna excluding the losses in the feeding network used for the measurement, particularly when the impedance match between the antenna and the feeding network is not perfect. A rigorous feeding network correction approach is introduced by using measurement data of the radiation efficiency of the whole antenna with feeding network and the \mbi S-matrices of both the feeding network and the antenna. As an example of this approach, the radiation efficiency of a multiport Eleven antenna has been determined and verified against the simulated results.

Effects of Mutual Coupling on LTE MIMO Capacity for Monopole Array: Comparing Reverberation Chamber Tests and Drive Tests

The roof of an automobile would appear to be an ideal platform to place multiple-input-multiple-output (MIMO) antennas, having a large ground plane with plenty of space to separate antennas for optimum embedded element radiation efficiency. However, styling concerns often require that the antennas are to be placed close together. Thus, mutual coupling plays an important role in the performance of an MIMO antenna system as it affects the embedded element efficiency and the channel correlation. In this letter, we present a comparison between the measured mutual coupling effect on the ergodic channel capacity of a 2 ×2 MIMO system in a reverberation chamber (i.e., Rayleigh channel) and in a suburban outdoor environment (i.e., Rician channel) at Long Term Evolution (LTE) radio band 13. The outdoor MIMO capacity was obtained during a vehicle drive test using commercial over-the-air (OTA) LTE test equipment. All measurements were conducted with two-element monopole antennas on a 24-in-diameter circular ground plane. The impact that mutual coupling has in the degradation of the embedded element radiation efficiency and increased correlation between the antennas, and ultimately the decrease in ergodic MIMO channel capacity, is highlighted by these measurements. In addition, the results provide insight into the differences of channel capacity obtained in the rich isotropic multipath environment of a reverberation chamber and the channel capacity obtained in a real-world suburban environment.

Efficiency, correlation, and diversity gain of UWB multiport self-grounded bow-tie antenna in rich isotropic multipath environment

The paper studies the performance of a novel ultra-wideband multiport self-grounded bow-tie antenna and presents simulated embedded radiation efficiencies and correlation at each antenna port, and the diversity gain of the antenna in rich isotropic multipath environment.

Diversity Gain Influenced by Polarization and Spatial Diversity Techniques in Ultrawideband

This paper presents an experimental investigation of diversity gain influenced by polarization and spatial diversity techniques in ultrawideband (UWB) radio technology. To this aim, two different coplanar-fed UWB diversity antennas having the same size and employing identical monopoles were taken and both effective and apparent diversity gain were measured in a reverberation chamber. To extract the diversity gain, three commonly used approaches to combine diversity (i.e., selection, equal gain, and maximal ratio) have been considered. Results showed that >1 dB (~ 26 %) improvement in diversity gain is obtained over most of the considered band for polarization diversity case as compared with spatial case, showing the usefulness of polarization diversity for future UWB diversity applications.

Modeling system throughput of single and multi-port wireless LTE devices

We have recently introduced a simple theoretical model for estimating the relative throughput of LTE devices. We validated the model through measurements performed in reverberation chamber for 1×2 SIMO with 90ns channel delay spread. In the present paper, we extend our previous study to compare the frequency diversity offered by different channel delay spreads emulated in reverberation chamber for SISO and 1×2 SIMO configurations.