Qiaowei Yuan

Modulated scattering array antenna for MIMO applications

Modulated scattering array antenna (MSAA) for MIMO applications is experimentally studied. The MSAA has a multi-antenna structure, but it is composed of only one normal antenna element together with several modulated scattering elements (MSE). The Error Vector Magnitude (EVM) which indicates the MIMO performance is measured in an indoor environment when a 2-element MSAA is used as the MIMO antenna in a 2 × 2 MIMO system. It is demonstrated that 2-stream data link can be established. However, the EVMs of the 2 streams are quite different and an averaged 7dB difference is observed due to the gain degradation of the MSE, indicating the MSAA can be used in the MIMO applications where simplifying the configuration of MIMO antenna system is taken high priority.

Experimental Study on MUSIC-Based DOA Estimation by Using Universal Steering Vector

MUSIC-based estimation of direction of arrival (DOA) using universal steering vector (USV) is experimentally studied. A four-element array antenna and a four-channel receiver are employed for the experiment. In order to improve the accuracy of DOA estimation, USV which has already included the effect of mutual coupling between array elements and effect of array elements themselves is compensated to further include the electric delay and loss of four channels in the receiver. The compensated USV (C-USV) approach proposed in this paper does not need the time-consuming measurement of array element pattern because the compensating matrix for USV is obtained by measuring the S parameters between RF input ports of the feeding cables and IF output ports of the receiver. The experimental results of MUSIC-based DOA estimation show that C-USV approach is an accurate, effective and practical method for the MUSIC-based DOA estimation.

Performance Study of W-CDMA Adaptive Array Antennas

The effect of the antenna geometry and the adaptive algorithm on the performance of a W-CDMA adaptive array antenna for mobile terminals is investigated experimentally. A W-CDMA receiving system for a 4-element array antenna is developed. The adaptive algorithm and the array antenna configuration are changed according to the requirement of the investigation. The performance of the system including synthesized pattern, adaptive weight and bit-error-rate (BER) characteristics are measured for the performance analysis. Results show that signal-to-interference ratio (SIR) can be greatly improved by 6 to 10 dB compared with the single antenna when BER is equal to 10-3. BER of the single monopole with a reflector is lower than that of the single monopole because the monopole with reflector has a higher gain in the direction of the desired wave. However, the SIR improvement of the monopole array is larger than that of the monopole array with a reflector because the array element gain of the monopole to the direction of the interference is larger. It seems that array elements which have homogeneous radiation pattern and high radiation efficiency are suitable to the adaptive array antennas

A hybrid method to obtain steering vector for music-based DOA estimation at the presence of mutual coupling and RF channel gain/phase errors

Multiple signal classification (MUSIC) is a highly popular eigenstructure-based estimation method of direction of arrival (DOA) with high resolution. The accuracy of the MUSIC-based DOA estimation is degraded significantly both by the effects of the mutual coupling among the receiving array elements and the unequal channel gain and phase errors of the receiver. Two approaches to evaluate the compensated USV (C-USV) are presented and further compared with the N-USV. The C-USV includes the effects not only from mutual coupling between array elements, but also from the unequal gain and phase response of RF cables and the receiver, while the N-USV is the numerical USV evaluated by methods of moment (MoM). Finally, the estimated results by the USVs are compared and the effectiveness of the C-USV by the hybrid method are demonstrated.

Measurement of diversity performance of modulated scattering array antennas for mobile handsets

Array antennas have been widely studied and used for base stations because they are effective in solving the problems of multipath fading and co-channel interference and improving performance and capacity in wireless communication systems. However, little effort has been made for developing array antennas suitable for mobile handsets, because of the difficulties such as the limited space on the handset to mount an antenna array with sufficiently low spatial correlation, high cost and complexity of the printed board circuits for operating adaptive algorithm. Therefore, it is required to develop array antennas with simple configurations which are suitable for mobile handsets. The modulated scattering technique was one of the effective measurement methods for near field measurement and was applied to fast measurement of antenna radiation pattern recently. A new concept of array antennas, which is called modulated scattering array antenna (MSAA), was proposed based on the modulated scattering technique. In this research, the diversity performance of a 2-element MSAA are measured in Raleigh fading environment to demonstrate the effectiveness of the MSAA.

Fixed gap source model for MoM analysis of linear antennas using sinusoidal reaction matching

The method of moment (MoM) using sinusoidal reaction matching has been used extensively in analyzing the thin wire antennas, because of its high accuracy and stability. In this article, the fixed gap source model is applied to the MoM analysis using sinusoidal reaction matching. The elements of the voltage vector corresponding to the feed are derived. This source model is applied to both the thin wire approximation (reduced kernel approximation) and the full kernel formulation. The results of the analysis are compared with the results of the conventional methods and measurement to show the accuracy of the proposed method.